Merge branch 'develop' into rav/fix_closed_connection_errors

synapse/config/tls.py

synapse/rest/media/v1/media_repository.py

synapse/rest/media/v1/preview_url_resource.py

synapse/rest/media/v1/thumbnail_resource.py

synapse/util/logcontext.py

tests/crypto/test_keyring.py

tests/util/test_logcontext.py