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

spec/lib/feed_manager_spec.rb

@@ -126,6 +126,14 @@ RSpec.describe FeedManager do
         reblog = Fabricate(:status, reblog: status, account: jeff)
         expect(FeedManager.instance.filter?(:home, reblog, alice.id)).to be true
       end
+
+      it 'returns true if status contains irreversibly muted phrase' do
+        alice.custom_filters.create!(phrase: 'farts', context: %w(home public), irreversible: true)
+        alice.custom_filters.create!(phrase: 'pop tarts', context: %w(home), irreversible: true)
+        alice.follow!(jeff)
+        status = Fabricate(:status, text: 'i sure like POP TARts', account: jeff)
+        expect(FeedManager.instance.filter?(:home, status, alice.id)).to be true
+      end
     end
 
     context 'for mentions feed' do