Add conversations API (#8832)

* Add conversations API

* Add web UI for conversations

* Add test for conversations API

* Add tests for ConversationAccount

* Improve web UI

* Rename ConversationAccount to AccountConversation

* Remove conversations on block and mute

* Change last_status_id to be a denormalization of status_ids

* Add optimistic locking

app/javascript/mastodon/reducers/notifications.js

@@ -69,7 +69,7 @@ const expandNormalizedNotifications = (state, notifications, next) => {
     }
 
     if (!next) {
-      mutable.set('hasMore', true);
+      mutable.set('hasMore', false);
     }
 
     mutable.set('isLoading', false);