### Pull Request Checklist

<!-- Please read
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before submitting your pull request -->

* [X] Pull request is based on the develop branch
* [X] Pull request includes a [changelog
file](https://element-hq.github.io/synapse/latest/development/contributing_guide.html#changelog).
The entry should:
- Be a short description of your change which makes sense to users.
"Fixed a bug that prevented receiving messages from other servers."
instead of "Moved X method from `EventStore` to `EventWorkerStore`.".
  - Use markdown where necessary, mostly for `code blocks`.
  - End with either a period (.) or an exclamation mark (!).
  - Start with a capital letter.
- Feel free to credit yourself, by adding a sentence "Contributed by
@github_username." or "Contributed by [Your Name]." to the end of the
entry.
* [X] [Code
style](https://element-hq.github.io/synapse/latest/code_style.html) is
correct
(run the
[linters](https://element-hq.github.io/synapse/latest/development/contributing_guide.html#run-the-linters)

)

---------

Co-authored-by: Andrew Morgan <1342360+anoadragon453@users.noreply.github.com>

Update version constraint to allow the latest `poetry-core` `1.9.1`

Context:

> I am working on updating poetry-core in Fedora and synapse is one of
affected packages. Please run a CI to see if it works properly. Thank
you.

Mergeable version of https://github.com/element-hq/synapse/pull/17848

### Pull Request Checklist

<!-- Please read
https://element-hq.github.io/synapse/latest/development/contributing_guide.html
before submitting your pull request -->

* [X] Pull request is based on the develop branch
* [X] Pull request includes a [changelog
file](https://element-hq.github.io/synapse/latest/development/contributing_guide.html#changelog).
The entry should:
- Be a short description of your change which makes sense to users.
"Fixed a bug that prevented receiving messages from other servers."
instead of "Moved X method from `EventStore` to `EventWorkerStore`.".
  - Use markdown where necessary, mostly for `code blocks`.
  - End with either a period (.) or an exclamation mark (!).
  - Start with a capital letter.
- Feel free to credit yourself, by adding a sentence "Contributed by
@github_username." or "Contributed by [Your Name]." to the end of the
entry.
* [X] [Code
style](https://element-hq.github.io/synapse/latest/code_style.html) is
correct
(run the
[linters](https://element-hq.github.io/synapse/latest/development/contributing_guide.html#run-the-linters))

Bumps
[actions/download-artifact](https://github.com/actions/download-artifact)
from 3 to 4.1.7.
<details>
<summary>Release notes</summary>
<p><em>Sourced from <a
href="https://github.com/actions/download-artifact/releases">actions/download-artifact's
releases</a>.</em></p>
<blockquote>
<h2>v4.1.7</h2>
<h2>What's Changed</h2>
<ul>
<li>Update <code>@​actions/artifact</code> dependency by <a
href="https://github.com/bethanyj28"><code>@​bethanyj28</code></a> in <a
href="https://redirect.github.com/actions/download-artifact/pull/325">actions/download-artifact#325</a></li>
</ul>
<p><strong>Full Changelog</strong>: <a
href="https://github.com/actions/download-artifact/compare/v4.1.6...v4.1.7">https://github.com/actions/download-artifact/compare/v4.1.6...v4.1.7</a></p>
<h2>v4.1.6</h2>
<h2>What's Changed</h2>
<ul>
<li>updating <code>@actions/artifact</code> dependency to v2.1.6 by <a
href="https://github.com/eggyhead"><code>@​eggyhead</code></a> in <a
href="https://redirect.github.com/actions/download-artifact/pull/324">actions/download-artifact#324</a></li>
</ul>
<p><strong>Full Changelog</strong>: <a
href="https://github.com/actions/download-artifact/compare/v4.1.5...v4.1.6">https://github.com/actions/download-artifact/compare/v4.1.5...v4.1.6</a></p>
<h2>v4.1.5</h2>
<h2>What's Changed</h2>
<ul>
<li>Update readme with v3/v2/v1 deprecation notice by <a
href="https://github.com/robherley"><code>@​robherley</code></a> in <a
href="https://redirect.github.com/actions/download-artifact/pull/322">actions/download-artifact#322</a></li>
<li>Update dependencies <code>@actions/core</code> to v1.10.1 and
<code>@actions/artifact</code> to v2.1.5</li>
</ul>
<p><strong>Full Changelog</strong>: <a
href="https://github.com/actions/download-artifact/compare/v4.1.4...v4.1.5">https://github.com/actions/download-artifact/compare/v4.1.4...v4.1.5</a></p>
<h2>v4.1.4</h2>
<h2>What's Changed</h2>
<ul>
<li>Update <code>@​actions/artifact</code> by <a
href="https://github.com/bethanyj28"><code>@​bethanyj28</code></a> in <a
href="https://redirect.github.com/actions/download-artifact/pull/307">actions/download-artifact#307</a></li>
</ul>
<p><strong>Full Changelog</strong>: <a
href="https://github.com/actions/download-artifact/compare/v4...v4.1.4">https://github.com/actions/download-artifact/compare/v4...v4.1.4</a></p>
<h2>v4.1.3</h2>
<h2>What's Changed</h2>
<ul>
<li>Update release-new-action-version.yml by <a
href="https://github.com/konradpabjan"><code>@​konradpabjan</code></a>
in <a
href="https://redirect.github.com/actions/download-artifact/pull/292">actions/download-artifact#292</a></li>
<li>Update toolkit dependency with updated unzip logic by <a
href="https://github.com/bethanyj28"><code>@​bethanyj28</code></a> in <a
href="https://redirect.github.com/actions/download-artifact/pull/299">actions/download-artifact#299</a></li>
<li>Update <code>@​actions/artifact</code> by <a
href="https://github.com/bethanyj28"><code>@​bethanyj28</code></a> in <a
href="https://redirect.github.com/actions/download-artifact/pull/303">actions/download-artifact#303</a></li>
</ul>
<h2>New Contributors</h2>
<ul>
<li><a
href="https://github.com/bethanyj28"><code>@​bethanyj28</code></a> made
their first contribution in <a
href="https://redirect.github.com/actions/download-artifact/pull/299">actions/download-artifact#299</a></li>
</ul>
<p><strong>Full Changelog</strong>: <a
href="https://github.com/actions/download-artifact/compare/v4...v4.1.3">https://github.com/actions/download-artifact/compare/v4...v4.1.3</a></p>
<h2>v4.1.2</h2>
<ul>
<li>Bump <code>@​actions/artifacts</code> to latest version to include
<a href="https://redirect.github.com/actions/toolkit/pull/1648">updated
GHES host check</a></li>
</ul>
<h2>v4.1.1</h2>
<ul>
<li>Fix transient request timeouts <a
href="https://redirect.github.com/actions/download-artifact/issues/249">actions/download-artifact#249</a></li>
<li>Bump <code>@actions/artifacts</code> to latest version</li>
</ul>
<h2>v4.1.0</h2>
<h2>What's Changed</h2>
<ul>
<li>Some cleanup by <a
href="https://github.com/robherley"><code>@​robherley</code></a> in <a
href="https://redirect.github.com/actions/download-artifact/pull/247">actions/download-artifact#247</a></li>
<li>Fix default for run-id by <a
href="https://github.com/stchr"><code>@​stchr</code></a> in <a
href="https://redirect.github.com/actions/download-artifact/pull/252">actions/download-artifact#252</a></li>
</ul>
<!-- raw HTML omitted -->
</blockquote>
<p>... (truncated)</p>
</details>
<details>
<summary>Commits</summary>
<ul>
<li><a
href="https://github.com/actions/download-artifact/commit/65a9edc5881444af0b9093a5e628f2fe47ea3b2e"><code>65a9edc</code></a>
Merge pull request <a
href="https://redirect.github.com/actions/download-artifact/issues/325">#325</a>
from bethanyj28/main</li>
<li><a
href="https://github.com/actions/download-artifact/commit/fdd1595981c1a29187d3de99c28c28a166bc38f7"><code>fdd1595</code></a>
licensed</li>
<li><a
href="https://github.com/actions/download-artifact/commit/c13dba102f4bb92b3f679fa086db9e2973960ca7"><code>c13dba1</code></a>
update <code>@​actions/artifact</code> dependency</li>
<li><a
href="https://github.com/actions/download-artifact/commit/0daa75ebeac4617faeb127496dbd716b8bcce26e"><code>0daa75e</code></a>
Merge pull request <a
href="https://redirect.github.com/actions/download-artifact/issues/324">#324</a>
from actions/eggyhead/use-artifact-v2.1.6</li>
<li><a
href="https://github.com/actions/download-artifact/commit/9c19ed7fe5d278cd354c7dfd5d3b88589c7e2395"><code>9c19ed7</code></a>
Merge branch 'main' into eggyhead/use-artifact-v2.1.6</li>
<li><a
href="https://github.com/actions/download-artifact/commit/3d3ea8741ef44e86f7392b41e391bde3c36219bd"><code>3d3ea87</code></a>
updating license</li>
<li><a
href="https://github.com/actions/download-artifact/commit/89af5db8211998d3ca691103a86b0b9362a94286"><code>89af5db</code></a>
updating artifact package v2.1.6</li>
<li><a
href="https://github.com/actions/download-artifact/commit/b4aefff88e83a2676a730654e1ce3dce61880379"><code>b4aefff</code></a>
Merge pull request <a
href="https://redirect.github.com/actions/download-artifact/issues/323">#323</a>
from actions/eggyhead/update-artifact-v215</li>
<li><a
href="https://github.com/actions/download-artifact/commit/8caf195ad4b1dee92908e23f56eeb0696f1dd42d"><code>8caf195</code></a>
package lock update</li>
<li><a
href="https://github.com/actions/download-artifact/commit/d7a2ec411d177e8ca679ac5969b70be59c322700"><code>d7a2ec4</code></a>
updating package version</li>
<li>Additional commits viewable in <a
href="https://github.com/actions/download-artifact/compare/v3...v4.1.7">compare
view</a></li>
</ul>
</details>
<br />


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Signed-off-by: dependabot[bot] <support@github.com>
Co-authored-by: dependabot[bot] <49699333+dependabot[bot]@users.noreply.github.com>
Co-authored-by: Devon Hudson <devonhudson@librem.one>

Use more correct changelog entries for refactoring `Generator` usage

 - https://github.com/element-hq/synapse/pull/17813
 - https://github.com/element-hq/synapse/pull/17814
 - https://github.com/element-hq/synapse/pull/17815
 - https://github.com/element-hq/synapse/pull/17816
 - https://github.com/element-hq/synapse/pull/17817

### Pull Request Checklist

<!-- Please read
https://element-hq.github.io/synapse/latest/development/contributing_guide.html
before submitting your pull request -->

* [x] Pull request is based on the develop branch
* [x] Pull request includes a [changelog
file](https://element-hq.github.io/synapse/latest/development/contributing_guide.html#changelog).
The entry should:
- Be a short description of your change which makes sense to users.
"Fixed a bug that prevented receiving messages from other servers."
instead of "Moved X method from `EventStore` to `EventWorkerStore`.".
  - Use markdown where necessary, mostly for `code blocks`.
  - End with either a period (.) or an exclamation mark (!).
  - Start with a capital letter.
- Feel free to credit yourself, by adding a sentence "Contributed by
@github_username." or "Contributed by [Your Name]." to the end of the
entry.
* [x] [Code
style](https://element-hq.github.io/synapse/latest/code_style.html) is
correct
(run the
[linters](https://element-hq.github.io/synapse/latest/development/contributing_guide.html#run-the-linters))

When entries insert in the end of timer queue, then unnecessary entry
inserted (with duplicated key).
This can lead to some timeouts expired early and consume memory.

Basically, if the client sets a special query param on `/sync` v2
instead of responding with `state` at the *start* of the timeline, we
instead respond with `state_after` at the *end* of the timeline.

We do this by using the `current_state_delta_stream` table, which is
actually reliable, rather than messing around with "state at" points on
the timeline.

c.f. MSC4222

```py
from twisted.web.http_headers import Headers

Headers()._canonicalNameCaps
Headers()._encodeName
```

Introduced in https://github.com/matrix-org/synapse/pull/15913 <-
https://github.com/matrix-org/synapse/pull/15773

Lazy-loading room members on incremental sync and remember which
memberships we've sent down the connection before (up-to 100)

Fix https://github.com/element-hq/synapse/issues/17804

https://github.com/matrix-org/matrix-spec-proposals/pull/4151 has
finished FCP.

See https://github.com/element-hq/synapse/issues/17373

 for unstable
endpoint removal

---------

Co-authored-by: Andrew Morgan <andrew@amorgan.xyz>

Context: https://github.com/matrix-org/synapse/issues/15439
(https://github.com/element-hq/synapse/issues/15439)

Also see discussion in https://github.com/element-hq/synapse/pull/17813

Context: https://github.com/matrix-org/synapse/issues/15439
(https://github.com/element-hq/synapse/issues/15439)

Also see discussion in https://github.com/element-hq/synapse/pull/17813

Context: https://github.com/matrix-org/synapse/issues/15439
(https://github.com/element-hq/synapse/issues/15439)

Also see discussion in https://github.com/element-hq/synapse/pull/17813

Context: https://github.com/matrix-org/synapse/issues/15439
(https://github.com/element-hq/synapse/issues/15439)

Also see discussion in https://github.com/element-hq/synapse/pull/17813

Context: https://github.com/matrix-org/synapse/issues/15439
(https://github.com/element-hq/synapse/issues/15439)

Also see discussion in https://github.com/element-hq/synapse/pull/17813

Fix #17819

The main change here is to add a helper function
`gather_optional_coroutines`, which works in a similar way as
`yieldable_gather_results` but takes a set of coroutines rather than a
function

Fixes #17823

While we're at it, makes a change where the redactions are sent as the
admin if the user is not a member of the server (otherwise these fail
with a "User must be our own" message).

This failed when install with poetry, so let's properly try and detect
what's going on.

To help debug problems such as
https://github.com/element-hq/synapse/issues/17822

Co-authored-by: dependabot[bot] <49699333+dependabot[bot]@users.noreply.github.com>

Co-authored-by: dependabot[bot] <49699333+dependabot[bot]@users.noreply.github.com>