Reference that the federation_reader needs the HTTP replication port set

Fix MAU invalidation due to missing yield

server notices on resource limit blocking

This was originally done in commit c75b71a3,
but got reverted on this branch due to the PR (#3677) being based on the wrong
branch.

We're ready to merge this to master now, so let's make it match
release-v0.33.3.

Features
--------

- Add support for the SNI extension to federation TLS connections. Thanks to @vojeroen! ([\#3439](https://github.com/matrix-org/synapse/issues/3439))
- Add /_media/r0/config ([\#3184](https://github.com/matrix-org/synapse/issues/3184))
- speed up /members API and add `at` and `membership` params as per MSC1227 ([\#3568](https://github.com/matrix-org/synapse/issues/3568))
- implement `summary` block in /sync response as per MSC688 ([\#3574](https://github.com/matrix-org/synapse/issues/3574))
- Add lazy-loading support to /messages as per MSC1227 ([\#3589](https://github.com/matrix-org/synapse/issues/3589))
- Add ability to limit number of monthly active users on the server ([\#3633](https://github.com/matrix-org/synapse/issues/3633))
- Support more federation endpoints on workers ([\#3653](https://github.com/matrix-org/synapse/issues/3653))
- Basic support for room versioning ([\#3654](https://github.com/matrix-org/synapse/issues/3654))
- Ability to disable client/server Synapse via conf toggle ([\#3655](https://github.com/matrix-org/synapse/issues/3655))
- Ability to whitelist specific threepids against monthly active user limiting ([\#3662](https://github.com/matrix-org/synapse/issues/3662))
- Add some metrics for the appservice and federation event sending loops ([\#3664](https://github.com/matrix-org/synapse/issues/3664))
- Where server is disabled, block ability for locked out users to read new messages ([\#3670](https://github.com/matrix-org/synapse/issues/3670))
- set admin uri via config, to be used in error messages where the user should contact the administrator ([\#3687](https://github.com/matrix-org/synapse/issues/3687))
- Synapse's presence functionality can now be disabled with the "use_presence" configuration option. ([\#3694](https://github.com/matrix-org/synapse/issues/3694))
- For resource limit blocked users, prevent writing into rooms ([\#3708](https://github.com/matrix-org/synapse/issues/3708))

Bugfixes
--------

- Fix occasional glitches in the synapse_event_persisted_position metric ([\#3658](https://github.com/matrix-org/synapse/issues/3658))
- Fix bug on deleting 3pid when using identity servers that don't support unbind API ([\#3661](https://github.com/matrix-org/synapse/issues/3661))
- Make the tests pass on Twisted < 18.7.0 ([\#3676](https://github.com/matrix-org/synapse/issues/3676))
- Don’t ship recaptcha_ajax.js, use it directly from Google ([\#3677](https://github.com/matrix-org/synapse/issues/3677))
- Fixes test_reap_monthly_active_users so it passes under postgres ([\#3681](https://github.com/matrix-org/synapse/issues/3681))
- Fix mau blocking calulation bug on login ([\#3689](https://github.com/matrix-org/synapse/issues/3689))
- Fix missing yield in synapse.storage.monthly_active_users.initialise_reserved_users ([\#3692](https://github.com/matrix-org/synapse/issues/3692))
- Improve HTTP request logging to include all requests ([\#3700](https://github.com/matrix-org/synapse/issues/3700))
- Avoid timing out requests while we are streaming back the response ([\#3701](https://github.com/matrix-org/synapse/issues/3701))
- Support more federation endpoints on workers ([\#3705](https://github.com/matrix-org/synapse/issues/3705), [\#3713](https://github.com/matrix-org/synapse/issues/3713))
- Fix "Starting db txn 'get_all_updated_receipts' from sentinel context" warning ([\#3710](https://github.com/matrix-org/synapse/issues/3710))
- Fix bug where `state_cache` cache factor ignored environment variables ([\#3719](https://github.com/matrix-org/synapse/issues/3719))
- Fix bug in v0.33.3rc1 which caused infinite loops and OOMs ([\#3723](https://github.com/matrix-org/synapse/issues/3723))
- Fix bug introduced in v0.33.3rc1 which made the ToS give a 500 error ([\#3732](https://github.com/matrix-org/synapse/issues/3732))

Deprecations and Removals
-------------------------

- The Shared-Secret registration method of the legacy v1/register REST endpoint has been removed. For a replacement, please see [the admin/register API documentation](https://github.com/matrix-org/synapse/blob/master/docs/admin_api/register_api.rst). ([\#3703](https://github.com/matrix-org/synapse/issues/3703))

Internal Changes
----------------

- The test suite now can run under PostgreSQL. ([\#3423](https://github.com/matrix-org/synapse/issues/3423))
- Refactor HTTP replication endpoints to reduce code duplication ([\#3632](https://github.com/matrix-org/synapse/issues/3632))
- Tests now correctly execute on Python 3. ([\#3647](https://github.com/matrix-org/synapse/issues/3647))
- Sytests can now be run inside a Docker container. ([\#3660](https://github.com/matrix-org/synapse/issues/3660))
- Port over enough to Python 3 to allow the sytests to start. ([\#3668](https://github.com/matrix-org/synapse/issues/3668))
- Update docker base image from alpine 3.7 to 3.8. ([\#3669](https://github.com/matrix-org/synapse/issues/3669))
- Rename synapse.util.async to synapse.util.async_helpers to mitigate async becoming a keyword on Python 3.7. ([\#3678](https://github.com/matrix-org/synapse/issues/3678))
- Synapse's tests are now formatted with the black autoformatter. ([\#3679](https://github.com/matrix-org/synapse/issues/3679))
- Implemented a new testing base class to reduce test boilerplate. ([\#3684](https://github.com/matrix-org/synapse/issues/3684))
- Rename MAU prometheus metrics ([\#3690](https://github.com/matrix-org/synapse/issues/3690))
- add new error type ResourceLimit ([\#3707](https://github.com/matrix-org/synapse/issues/3707))
- Logcontexts for replication command handlers ([\#3709](https://github.com/matrix-org/synapse/issues/3709))
- Update admin register API documentation to reference a real user ID. ([\#3712](https://github.com/matrix-org/synapse/issues/3712))

Allow guests to use /rooms/:roomId/event/:eventId

Allow profile updates to happen on workers

Refactor state module to support multiple room versions

limt -> limit

Fix 500 error from /consent form

Splits the state_group_cache in two.

One half contains normal state events; the other contains member events.

The idea is that the lazyloading common case of: "I want a subset of member events plus all of the other state" can be accomplished efficiently by splitting the cache into two, and asking for "all events" from the non-members cache, and "just these keys" from the members cache.  This means we can avoid having to make DictionaryCache aware of these sort of complicated queries, whilst letting LL requests benefit from the caching.

Previously we were unable to sensibly use the caching and had to pull all state from the DB irrespective of the filtering, which made things slow.  Hopefully fixes https://github.com/matrix-org/synapse/issues/3720.

Fixes #3731

Bugfixes
--------

- Fix bug in v0.33.3rc1 which caused infinite loops and OOMs
([\#3723](https://github.com/matrix-org/synapse/issues/3723))

Don't log exceptions when failing to fetch server keys

LaterGauge needs to call thread safe functions

Not being able to resolve or connect to remote servers is an expected
error, so we shouldn't log at ERROR with stacktraces.

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