Added shields directing to synapse-dev room, showing license, latest version on PyPi and supported Python versions.
I've moved substitution definitions to the bottom to improve readability.

Signed-off-by: Mateusz Przybyłowicz <uamfhq@gmail.com>

This turns:

    Failed to parse config for 'myplugin': Exception('error message')

into:

    Failed to parse config for 'myplugin': error message.

We call `_update_stream_positions_table_txn` a lot, which is an UPSERT
that can conflict in `REPEATABLE READ` isolation level. Instead of doing
a transaction consisting of a single query we may as well run it outside
of a transaction.

By reporting the log level of the synapse logger as a string.

We call `_update_stream_positions_table_txn` a lot, which is an UPSERT
that can conflict in `REPEATABLE READ` isolation level. Instead of doing
a transaction consisting of a single query we may as well run it outside
of a transaction.

Currently when using multiple event persisters we (in the worst case) don't tell clients about events until all event persisters have persisted new events after the original event. This is a suboptimal, especially if one of the event persisters goes down.

To handle this, we encode the position of each event persister in the room tokens so that we can send events to clients immediately. To reduce the size of the token we do two things:

1. We create a unique immutable persistent mapping between instance names and a generated small integer ID, which we can encode in the tokens instead of the instance name; and
2. We encode the "persisted upto position" of the room token and then only explicitly include instances that have positions strictly greater than that.

The new tokens look something like: `m3478~1.3488~2.3489`, where the first number is the min position, and the subsequent `-` separated pairs are the instance ID to positions map. (We use `.` and `~` as separators as they're URL safe and not already used by `StreamToken`).

It seems most of these blacklisted tests do actually pass most of the time.

I'm of the opinion that having them blacklisted here means there is very little incentive for us to deflake any flaky tests, and meanwhile any value in those tests is completely lost.

This allows a user to store an offline device on the server and
then restore it at a subsequent login.

Reduce inconsistencies between codepaths for membership and non-membership events.

Lots of different module apis is not easy to maintain.

Rather than adding yet another ModuleApi(hs, hs.get_auth_handler()) incantation, first add an hs.get_module_api() method and use it where possible.

https://github.com/matrix-org/synapse/tree/develop/docs/sphinx doesn't seem to really be utilised or changed recently since the initial commit. I like the idea of exportable documentation of the codebase, but at the moment after running through the build instructions the generated website wasn't very useful...

* Optimise and test state fetching for 3p event rules

Getting all the events at once is much more efficient than getting them
individually

* Test that 3p event rules can modify events

Fix third-party event modules for `check_visibility_can_be_modified` check

This PR ports the quick fix from https://github.com/matrix-org/synapse/pull/2796 to further methods which handle media, URL preview and `/key/v2/server` requests. This prevents a harmless `ERROR` that comes up in the logs when we were unable to respond to a client request when the client had already disconnected. In this case we simply bail out if the client has already done so.

This is the 'simple fix' as suggested by https://github.com/matrix-org/synapse/issues/5304#issuecomment-574740003.

Fixes https://github.com/matrix-org/synapse/issues/6700
Fixes https://github.com/matrix-org/synapse/issues/5304

Per https://github.com/matrix-org/matrix-doc/pull/2788

PR #8292 tried to maintain backwards compat with modules which don't provide a
`check_visibility_can_be_modified` method, but the tests weren't being run,
and the check didn't work.

This is now redundant, and we can just call `handle_new_client_event` directly.

move the "duplicate state event" handling down into `handle_new_client_event`
where it can be shared between multiple call paths.

This fixes a bug when backfilling invalid events.

This PR allows `ThirdPartyEventRules` modules to view, manipulate and block changes to the state of whether a room is published in the public rooms directory.

While the idea of whether a room is in the public rooms list is not kept within an event in the room, `ThirdPartyEventRules` generally deal with controlling which modifications can happen to a room. Public rooms fits within that idea, even if its toggle state isn't controlled through a state event. 

There's no need for it to be in the dict as well as the events table. Instead,
we store it in a separate attribute in the EventInternalMetadata object, and
populate that on load.

This means that we can rely on it being correctly populated for any event which
has been persited to the database.

This fixes a bug where `m.ignored_user_list` was assumed to be a dict,
leading to odd behavior for users who set it to something else.

This is so we can tell what is going on when things are taking a while to start up.

The main change here is to ensure that transactions that are created during startup get correctly logged like normal transactions.

Synapse 1.21.0rc2 (2020-10-02)
==============================

Features
--------

- Convert additional templates from inline HTML to Jinja2 templates. ([\#8444](https://github.com/matrix-org/synapse/issues/8444))

Bugfixes
--------

- Fix a regression in v1.21.0rc1 which broke thumbnails of remote media. ([\#8438](https://github.com/matrix-org/synapse/issues/8438))
- Do not expose the experimental `uk.half-shot.msc2778.login.application_service` flow in the login API, which caused a compatibility problem with Element iOS. ([\#8440](https://github.com/matrix-org/synapse/issues/8440))
- Fix malformed log line in new federation "catch up" logic. ([\#8442](https://github.com/matrix-org/synapse/issues/8442))
- Fix DB query on startup for negative streams which caused long start up times. Introduced in [\#8374](https://github.com/matrix-org/synapse/issues/8374). ([\#8447](https://github.com/matrix-org/synapse/issues/8447))