Attempt to update the appropriate `m.room.aliases` event after deleting
an alias. This may fail due to the deleter not being in the room.

Will also check if the canonical alias of the event is set to the
deleted alias, and if so will attempt to delete it.

Make registration idempotent

Make registration idempotent: if you specify the same session, make it give you an access token for the user that was registered on previous uses of that session. Tweak the UI auth layer to not delete sessions when their auth has completed and hence expire themn so they don't hang around until server restart. Allow server-side data to be associated with UI auth sessions.

Add replication stream for pushers

Password reset docs and script

Add a comment to offer a hint to an explanation for why we have a unique constraint on (app_id, pushkey, user_id)

Replace the bash/perl gen_password script with a python one, and write a note
on how to use it.

Persist rejection of invites over federation

Add config to create guest account on 3pid invite

Currently, when a 3pid invite request is sent to an identity server, it
includes a provisioned guest access token. This allows the link in the,
say, invite email to include the guest access token ensuring that the
same account is used each time the link is clicked.

This flow has a number of flaws, including when using different servers
or servers that have guest access disabled.

For now, we keep this implementation but hide it behind a config option
until a better flow is implemented.

Fix regression where synapse checked whether push rules were valid

Fix regression where synapse checked whether push rules were valid JSON before the compatibility hack that handled clients sending invalid JSON

Implement logout

Use parse_json_object_from_request to parse JSON out of request bodies

Fix logout on password change

Make select more sensible when dseleting access tokens, rename pusher deletion to match access token deletion and make exception arg optional.

Delete old, unused methods and rename new one to just be `user_delete_access_tokens` with an `except_token_ids` argument doing what it says on the tin.