Merge branch 'develop' into babolivier/message_retention

...s/main/schema/delta/56/event_labels_background_update.sql

synapse/storage/data_stores/main/state.py

synapse/storage/data_stores/main/stream.py

synapse/storage/data_stores/main/tags.py

synapse/storage/prepare_database.py

synapse/storage/purge_events.py

synapse/streams/config.py

synapse/util/caches/descriptors.py

synapse/util/httpresourcetree.py

tests/handlers/test_federation.py

tests/rest/admin/test_admin.py

tests/rest/client/v1/test_rooms.py

tests/rest/media/v1/test_url_preview.py

tests/server.py

tests/storage/test_purge.py

tests/test_phone_home.py

tests/test_state.py

tox.ini