Keyword/phrase filtering (#7905)

* Add keyword filtering

    GET|POST       /api/v1/filters
    GET|PUT|DELETE /api/v1/filters/:id

- Irreversible filters can drop toots from home or notifications
- Other filters can hide toots through the client app
- Filters use a phrase valid in particular contexts, expiration

* Make sure expired filters don't get applied client-side

* Add missing API methods

* Remove "regex filter" from column settings

* Add tests

* Add test for FeedManager

* Add CustomFilter test

* Add UI for managing filters

* Add streaming API event to allow syncing filters

* Fix tests

app/javascript/mastodon/actions/streaming.js

@@ -6,6 +6,7 @@ import {
   disconnectTimeline,
 } from './timelines';
 import { updateNotifications, expandNotifications } from './notifications';
+import { fetchFilters } from './filters';
 import { getLocale } from '../locales';
 
 const { messages } = getLocale();
@@ -30,6 +31,9 @@ export function connectTimelineStream (timelineId, path, pollingRefresh = null)
         case 'notification':
           dispatch(updateNotifications(JSON.parse(data.payload), messages, locale));
           break;
+        case 'filters_changed':
+          dispatch(fetchFilters());
+          break;
         }
       },
     };