Merge pull request #2854 from matrix-org/erikj/event_create_worker

docs/workers.rst

synapse/app/event_creator.py

synapse/app/homeserver.py

synapse/config/workers.py

synapse/events/snapshot.py

synapse/handlers/message.py

synapse/replication/http/__init__.py

synapse/replication/http/send_event.py

synapse/replication/slave/storage/events.py

synapse/rest/client/v1/room.py

synapse/storage/appservice.py

synapse/types.py