This only makes a difference for versions of ldap3 before 1.0, but a)
its best to be explicit and b) there are distributions that package
ancient versions for ldap3 (e.g. debian).

Update documentation about exported prometheus metrics

Remove long-deprecated instructions about promethesus console; also fix for modern config file format

Bugfix for process-wide metric export on split processes

Pass the Metrics group into the process collector instead of having it find its own one; this avoids it needing to import from synapse.metrics

Fix user_threepids schema delta

The delta `37/user_threepids.sql` aimed to update all the email
addresses to be lower case, however duplicate emails may exist in the
table already.

This commit adds a step where the delta moves the duplicate emails to a
new `medium` `email_old`. Only the most recently used account keeps the
binding intact. We move rather than delete so that we retain some record
of which emails were associated with which account.

Allow clients to supply access_tokens as headers

Fix infinite typing bug

There's a bug somewhere that causes typing notifications to not be timed
out properly. By adding a paranoia timer and using correct inequalities
notifications should stop being stuck, even if it the root cause hasn't
been fixed.

Fix incredibly slow back pagination query

If a client didn't specify a from token when paginating backwards
synapse would attempt to query the (global) maximum topological token.
This a) doesn't make much sense since they're room specific and b) there
are no indices that lets postgres do this efficiently.

Standardise prometheus metrics

Allow Configurable Rate Limiting Per AS

This means synapse does not have to check if the AS is interested, but instead it effectively re-uses what it already knew about the requesting user