Use the actual origin for push transactions, rather than whatever the remote
server claimed.

We should check that both the sender's server, and the server which created the
event_id (which may be different from whatever the remote server has told us
the origin is), have signed the event.

Fix 500 error from /consent form

Fixes #3731

Fix exceptions when a connection is closed before we read the headers

This fixes bugs introduced in #3700, by making sure that we behave sanely
when an incoming connection is closed before the headers are read.

Make the logcontext filter not explode if it somehow ends up with a logcontext
of None, since that infinite-loops the whole logging system.

Use get_cache_factor_for function for `state_cache`

This allows the cache factor for `state_cache` to be individually
specified in the enviroment

Fix logging bug in EDU handling over replication

Logcontexts for replication command handlers

Fix logcontexts for running pushers

Use a producer to stream back responses

Refactor request logging code

add new error type ResourceLimit

Merge branch 'neilj/limit_exceeded_error' of github.com:matrix-org/synapse into neilj/limit_exceeded_error

Neilj/resource limit block event creation

Update the admin register documentation to return a real user ID

Presumably this is the intention anyways. I've also updated the domain part to be something more along the lines of what people might expect.