Pull out `twitter:` meta tags when generating a preview and
use it to augment any `og:` meta tags.

Prefers Open Graph information over Twitter card information.

Avoid breaking a URL preview completely if the chosen image 404s
or is unreachable for some other reason (e.g. DNS).

* Skip `og` and `meta` tags where the value is empty.
* Fallback to the favicon if there are no other images.
* Ignore tags meant for navigation.

By using urljoin from the standard library and reducing the number
of places URLs are rebased.

Co-authored-by: Patrick Cloke <clokep@users.noreply.github.com>

* Add type hints to `tests/rest`

* newsfile

* change import from `SigningKey`

The presence of this method was confusing, and mostly present for backwards
compatibility. Let's get rid of it.

Part of #11733

This implements an allow list for content types for which Synapse will attempt URL preview. If a URL resolves to a resource with a content type which isn't in the list, the download will terminate immediately.

This makes sense given that Synapse would never successfully generate a URL preview for such files in the first place, and helps prevent issues with streaming media servers, such as #8302.

Signed-off-by: Denis Kasak <dkasak@termina.org.uk>

Images which are data URLs will no longer break URL
previews and will properly be "downloaded" and
thumbnailed.

This reverts commit 158d73eb.

* Splits the logic for parsing HTML from the resource handling code.
* Fix a circular import in the oEmbed code (which uses the HTML parsing code).
* Renames some of the HTML parsing methods to:
  * Make it clear which methods are "internal" to the module.
  * Clarify what the methods do.

Revert "Sort internal changes in changelog"
Revert "Update CHANGES.md"
Revert "1.49.0rc1"
Revert "Revert "Move `glob_to_regex` and `re_word_boundary` to `matrix-python-common` (#11505) (#11527)"
Revert "Refactors in `_generate_sync_entry_for_rooms` (#11515)"
Revert "Correctly register shutdown handler for presence workers (#11518)"
Revert "Fix `ModuleApi.looping_background_call` for non-async functions (#11524)"
Revert "Fix 'delete room' admin api to work on incomplete rooms (#11523)"
Revert "Correctly ignore invites from ignored users (#11511)"
Revert "Fix the test breakage introduced by #11435 as a result of concurrent PRs (#11522)"
Revert "Stabilise support for MSC2918 refresh tokens as they have now been merged into the Matrix specification. (#11435)"
Revert "Save the OIDC session ID (sid) with the device on login (#11482)"
Revert "Add admin API to get some information about federation status (#11407)"
Revert "Include bundled aggregations in /sync and related fixes (#11478)"
Revert "Move `glob_to_regex` and `re_word_boundary` to `matrix-python-common` (#11505)"
Revert "Update backward extremity docs to make it clear that it does not indicate whether we have fetched an events' `prev_events` (#11469)"
Revert "Support configuring the lifetime of non-refreshable access tokens separately to refreshable access tokens. (#11445)"
Revert "Add type hints to `synapse/tests/rest/admin` (#11501)"
Revert "Revert accidental commits to develop."
Revert "Newsfile"
Revert "Give `tests.server.setup_test_homeserver` (nominally!) the same behaviour"
Revert "Move `tests.utils.setup_test_homeserver` to `tests.server`"
Revert "Convert one of the `setup_test_homeserver`s to `make_test_homeserver_synchronous`"
Revert "Disambiguate queries on `state_key` (#11497)"
Revert "Comments on the /sync tentacles (#11494)"
Revert "Clean up tests.storage.test_appservice (#11492)"
Revert "Clean up `tests.storage.test_main` to remove use of legacy code. (#11493)"
Revert "Clean up `tests.test_visibility` to remove legacy code. (#11495)"
Revert "Minor cleanup on recently ported doc pages  (#11466)"
Revert "Add most of the missing type hints to `synapse.federation`. (#11483)"
Revert "Avoid waiting for zombie processes in `synctl stop` (#11490)"
Revert "Fix media repository failing when media store path contains symlinks (#11446)"
Revert "Add type annotations to `tests.storage.test_appservice`. (#11488)"
Revert "`scripts-dev/sign_json`: support for signing events (#11486)"
Revert "Add MSC3030 experimental client and federation API endpoints to get the closest event to a given timestamp (#9445)"
Revert "Port wiki pages to documentation website (#11402)"
Revert "Add a license header and comment. (#11479)"
Revert "Clean-up get_version_string (#11468)"
Revert "Link background update controller docs to summary (#11475)"
Revert "Additional type hints for config module. (#11465)"
Revert "Register the login redirect endpoint for v3. (#11451)"
Revert "Update openid.md"
Revert "Remove mention of OIDC certification from Dex (#11470)"
Revert "Add a note about huge pages to our Postgres doc (#11467)"
Revert "Don't start Synapse master process if `worker_app` is set (#11416)"
Revert "Expose worker & homeserver as entrypoints in `setup.py` (#11449)"
Revert "Bundle relations of relations into the `/relations` result. (#11284)"
Revert "Fix `LruCache` corruption bug with a `size_callback` that can return 0 (#11454)"
Revert "Eliminate a few `Any`s in `LruCache` type hints (#11453)"
Revert "Remove unnecessary `json.dumps` from `tests.rest.admin` (#11461)"
Revert "Merge branch 'master' into develop"

This reverts commit 26b5d232.
This reverts commit bce4220f.
This reverts commit 966b5d0f.
This reverts commit 088d748f.
This reverts commit 14d593f7.
This reverts commit 2a3ec6fa.
This reverts commit eccc49d7.
This reverts commit b1ecd19c.
This reverts commit 9c55dedc.
This reverts commit 2d42e586.
This reverts commit 2f053f3f.
This reverts commit a15a893d.
This reverts commit 8b4b153c.
This reverts commit 494ebd73.
This reverts commit a77c3698.
This reverts commit 4eb77965.
This reverts commit 637df95d.
This reverts commit e5f426cd.
This reverts commit 8cd68b81.
This reverts commit 6cae125e.
This reverts commit 7be88fbf.
This reverts commit b3fd99b7.
This reverts commit f7ec6e7d.
This reverts commit 5640992d.
This reverts commit d26808dd.
This reverts commit f91624a5.
This reverts commit 16d39a54.
This reverts commit 8a4c2969.
This reverts commit 49e1356e.
This reverts commit d2279f47.
This reverts commit b50e39df.
This reverts commit 858d80bf.
This reverts commit 435f0448.
This reverts commit f61462e1.
This reverts commit a6f1a3ab.
This reverts commit 84dc50e1.
This reverts commit ed635d32.
This reverts commit 7b62791e.
This reverts commit 153194c7.
This reverts commit f44d729d.
This reverts commit a265fbd3.
This reverts commit b9fef1a7.
This reverts commit b0eb64ff.
This reverts commit f1795463.
This reverts commit 70cbb1a5.
This reverts commit 42bf0204.
This reverts commit 379f2650.
This reverts commit 7ff22d6d.
This reverts commit 5a0b652d.
This reverts commit 432a174b.
This reverts commit b14f8a1b, reversing
changes made to e713855d.

Also tighten validation of server names by forbidding invalid characters
in IPv6 addresses and empty domain labels.

* add code to handle missing content-type header and a test to verify that it works

* add handling for missing content-type in the /upload endpoint as well

* slightly refactor test code to put private method in approriate place

* handle possible null value for content-type when pulling from the local db

* add changelog

* refactor test and add code to handle missing content-type in cached remote media

* requested changes

* Update changelog.d/11200.bugfix

Co-authored-by: Sean Quah <8349537+squahtx@users.noreply.github.com>

Co-authored-by: Sean Quah <8349537+squahtx@users.noreply.github.com>

Searches the returned HTML for an oEmbed endpoint using the
autodiscovery mechanism (`<link rel=...>`), and will request it
to generate the preview.

URL cache files are short-lived and it does not make sense to offload
them (eg. to the cloud) or back them up.

* Improved titles (fall back to the author name if there's not title) and include the site name.
* Handle photo/video payloads.
* Include the original URL in the Open Graph response.
* Fix the expiration time (by properly converting from seconds to milliseconds).

The major change is moving the decision of whether to use oEmbed
further up the call-stack. This reverts the _download_url method to
being a "dumb" functionwhich takes a single URL and downloads it
(as it was before #7920).

This also makes more minor refactorings:

* Renames internal variables for clarity.
* Factors out shared code between the HTML and rich oEmbed
  previews.
* Fixes tests to preview an oEmbed image.

To avoid duplicating it between a few tests.

This adds the format to the request arguments / URL to
ensure that JSON data is returned (which is all that
Synapse supports).

This also adds additional error checking / filtering to the
configuration file to ignore XML-only providers.

This adds configuration options (under an `oembed` section) to
configure which URLs are matched to use oEmbed for URL
previews.

Fixes #10318

This PR adds a common configuration section for all modules (see docs). These modules are then loaded at startup by the homeserver. Modules register their hooks and web resources using the new `register_[...]_callbacks` and `register_web_resource` methods of the module API.

Part of #9744

Removes all redundant `# -*- coding: utf-8 -*-` lines from files, as python 3 automatically reads source code as utf-8 now.

`Signed-off-by: Jonathan de Jong <jonathan@automatia.nl&gt;`>

Properly uses RGBA mode for 1- and 8-bit images with transparency
(instead of RBG mode).

 - Update black version to the latest
 - Run black auto formatting over the codebase
    - Run autoformatting according to [`docs/code_style.md
`](https://github.com/matrix-org/synapse/blob/80d6dc9783aa80886a133756028984dbf8920168/docs/code_style.md)
 - Update `code_style.md` docs around installing black to use the correct version