See #1100: clean compat and XXX in the code

api/config/api_urls.py

api/config/routing.py

api/config/settings/common.py

api/funkwhale_api/common/dynamic_preferences_registry.py

api/funkwhale_api/common/fields.py

api/funkwhale_api/common/middleware.py

api/funkwhale_api/common/serializers.py

api/funkwhale_api/favorites/filters.py

api/funkwhale_api/federation/dynamic_preferences_registry.py

api/funkwhale_api/federation/serializers.py

api/funkwhale_api/federation/utils.py

...hale_api/moderation/migrations/0006_auto_20200803_1222.py

api/funkwhale_api/music/models.py

api/funkwhale_api/music/serializers.py

api/funkwhale_api/music/tasks.py

api/funkwhale_api/music/views.py

api/funkwhale_api/playlists/dynamic_preferences_registry.py

api/funkwhale_api/playlists/filters.py

api/funkwhale_api/playlists/models.py

...unkwhale_api/radios/migrations/0005_auto_20200803_1222.py