Merge branch 'master' into glitch-soc/merge-upstream

Conflicts:
- app/models/media_attachment.rb
  Upstream added audio attachment support
- app/serializers/initial_state_serializer.rb
  Upstream added audio attachment support and how mimetypes are returned
- app/serializers/rest/instance_serializer.rb
  Upstream added a few fields
- config/application.rb
  Upstream added a different paperclip transcoder

.env.production.sample

@@ -175,9 +175,6 @@ STREAMING_CLUSTER_NUM=1
 # MAX_IMAGE_SIZE=8388608
 # MAX_VIDEO_SIZE=41943040
 
-# Maximum length of audio uploads in seconds
-# MAX_AUDIO_LENGTH=60
-
 # LDAP authentication (optional)
 # LDAP_ENABLED=true
 # LDAP_HOST=localhost