Merge branch 'develop' into babolivier/message_retention

synapse/app/federation_sender.py

synapse/app/homeserver.py

synapse/appservice/api.py

synapse/config/appservice.py

synapse/config/captcha.py

synapse/config/emailconfig.py

synapse/config/room_directory.py

synapse/config/server.py

synapse/events/snapshot.py

synapse/federation/federation_client.py

synapse/federation/persistence.py

synapse/federation/sender/__init__.py

synapse/federation/sender/transaction_manager.py

synapse/federation/transport/__init__.py

synapse/federation/transport/client.py

synapse/federation/transport/server.py

synapse/handlers/auth.py

synapse/handlers/directory.py

synapse/handlers/e2e_keys.py

synapse/handlers/federation.py