Merge branch 'develop' into babolivier/mark_unread

CHANGES.md

changelog.d/7606.bugfix

changelog.d/7639.feature

changelog.d/7652.doc

changelog.d/7657.misc

changelog.d/7663.bugfix

changelog.d/7664.misc

debian/changelog

docs/sample_config.yaml

synapse/__init__.py

synapse/api/constants.py

synapse/config/cache.py

synapse/config/homeserver.py

synapse/config/room.py

synapse/config/saml2_config.py

synapse/config/server.py

synapse/handlers/federation.py

synapse/handlers/room.py

synapse/rest/client/v1/presence.py

synapse/static/client/login/index.html