* commit '3950ae51e':
  Ensure that remove_pusher is always async (#7981)
  Ensure the msg property of HttpResponseException is a string. (#7979)
  Remove from the event_relations table when purging historical events. (#7978)
  Add additional logging for SAML sessions. (#7971)
  Add MSC reference to changelog for #7736
  Re-implement unread counts (#7736)
  Various improvements to the docs (#7899)
  Convert storage layer to async/await. (#7963)
  Add an option to disable purge in delete room admin API (#7964)
  Move some log lines from default logger to sql/transaction loggers (#7952)
  Use the JSON module from the std library instead of simplejson. (#7936)
  Fix exit code for `check_line_terminators.sh` (#7970)
  Option to allow server admins to join complex rooms (#7902)
  Fix typo in metrics docs (#7966)
  Add script for finding files with unix line terminators (#7965)
  Convert the remaining media repo code to async / await. (#7947)
  Convert a synapse.events to async/await. (#7949)
  Convert groups and visibility code to async / await. (#7951)
  Convert push to async/await. (#7948)