The field is never read from, and all the opportunities given to populate it are not utilized. It should be very safe to remove this.

might help us figure out if https://github.com/vector-im/riot-web/issues/3868
has happened.

When a client retries a key upload, don't give an error if the signature has
changed (but the key is the same).

Fixes https://github.com/vector-im/riot-android/issues/1208, hopefully.

rather than having to instrument everywhere we make a federation call,
make the MatrixFederationHttpClient manage the retry limiter.

This was broken when device list updates were implemented, as Mailer
could no longer instantiate an AuthHandler due to a dependency on
federation sending.

The 'time' caveat on the access tokens was something of a lie, since we weren't
enforcing it; more pertinently its presence stops us ever adding useful time
caveats.

Let's move in the right direction by not lying in our caveats.

Signed-off-by: Patrik Oldsberg <patrik.oldsberg@ericsson.com>

Specifically, if currently_active remains true then we should not notify
if only the last active time changes.

This is for two reasons:

1. Suppresses duplicates correctly, as the notifier doesn't do any
   duplicate suppression.
2. Makes it easier to connect the AppserviceHandler to the replication
   stream.