Implement part [MSC2228](https://github.com/matrix-org/matrix-doc/pull/2228). The parts that differ are:
* the feature is hidden behind a configuration flag (`enable_ephemeral_messages`)
* self-destruction doesn't happen for state events
* only implement support for the `m.self_destruct_after` field (not the `m.self_destruct` one)
* doesn't send synthetic redactions to clients because for this specific case we consider the clients to be able to destroy an event themselves, instead we just censor it (by pruning its JSON) in the database
This fixed the weirdness of 400 vs 404 as http status code in the case
the filter id is not known by the server.
As e.g. matrix-js-sdk expects 404 to catch this situation this leads
to unwanted behaviour.
Pull the checkers out to their own classes, rather than having them lost in a
massive 1000-line class which does everything.
This is also preparation for some more intelligent advertising of flows, as per #6100
because, frankly, it looked like it was written by an axe-murderer.
This should be a non-functional change, except that where `m.login.dummy` was
previously advertised *before* `m.login.terms`, it will now be advertised
afterwards. AFAICT that should have no effect, and will be more consistent with
the flows that involve passing a 3pid.
Python will return a tuple whether there are parentheses around the returned values or not.
I'm just sick of my editor complaining about this all over the place :)
We can now use `_get_events_from_cache_or_db` rather than going right back to
the database, which means that (a) we can benefit from caching, and (b) it
opens the way forward to more extensive checks on the original event.
We now always require the original event to exist before we will serve up a
redaction.
When asking for the relations of an event, include the original event in the response. This will mostly be used for efficiently showing edit history, but could be useful in other circumstances.
When enabling the account validity feature, Synapse will look at startup for registered account without an expiration date, and will set one equals to 'now + validity_period' for them. On large servers, it can mean that a large number of users will have the same expiration date, which means that they will all be sent a renewal email at the same time, which isn't ideal.
In order to mitigate this, this PR allows server admins to define a 'max_delta' so that the expiration date is a random value in the [now + validity_period ; now + validity_period + max_delta] range. This allows renewal emails to be progressively sent over a configured period instead of being sent all in one big batch.
Replaces DEFAULT_ROOM_VERSION constant with a method that first checks the config, then returns a hardcoded value if the option is not present.
That hardcoded value is now located in the server.py config file.
If account validity is enabled in the server's configuration, this job will run at startup as a background job and will stick an expiration date to any registered account missing one.
This commit adds two config options:
* `restrict_public_rooms_to_local_users`
Requires auth to fetch the public rooms directory through the CS API and disables fetching it through the federation API.
* `require_auth_for_profile_requests`
When set to `true`, requires that requests to `/profile` over the CS API are authenticated, and only returns the user's profile if the requester shares a room with the profile's owner, as per MSC1301.
MSC1301 also specifies a behaviour for federation (only returning the profile if the server asking for it shares a room with the profile's owner), but that's currently really non-trivial to do in a not too expensive way. Next step is writing down a MSC that allows a HS to specify which user sent the profile query. In this implementation, Synapse won't send a profile query over federation if it doesn't believe it already shares a room with the profile's owner, though.
Groups have been intentionally omitted from this commit.
