Introduce action creators

These can be used to dispatch actions immediately, or after some asynchronous
work has been done. Also, create GroupActions.fetchJoinedGroups as an example.

The concept of async action creators can be used in the following cases:
 - stores or views that do async work, dispatching based on the results
 - actions that have complicated payloads, would make more sense as functions
   with documentation that dispatch created actions.

src/components/structures/TagPanel.js

@@ -20,6 +20,9 @@ import { MatrixClient } from 'matrix-js-sdk';
 import FilterStore from '../../stores/FilterStore';
 import FlairStore from '../../stores/FlairStore';
 import TagOrderStore from '../../stores/TagOrderStore';
+
+import GroupActions from '../../actions/GroupActions';
+
 import sdk from '../../index';
 import dis from '../../dispatcher';
 
@@ -62,8 +65,8 @@ const TagPanel = React.createClass({
                 this.setState({orderedGroupTagProfiles});
             });
         });
-
-        this._fetchJoinedRooms();
+        // This could be done by anything with a matrix client
+        GroupActions.fetchJoinedGroups(this.context.matrixClient);
     },
 
     componentWillUnmount() {
@@ -76,7 +79,7 @@ const TagPanel = React.createClass({
 
     _onGroupMyMembership() {
         if (this.unmounted) return;
-        this._fetchJoinedRooms();
+        GroupActions.fetchJoinedGroups(this.context.matrixClient);
     },
 
     onClick() {
@@ -88,16 +91,6 @@ const TagPanel = React.createClass({
         dis.dispatch({action: 'view_create_group'});
     },
 
-    async _fetchJoinedRooms() {
-        // This could be done by anything with a matrix client (, see TagOrderStore).
-        const joinedGroupResponse = await this.context.matrixClient.getJoinedGroups();
-        const joinedGroupIds = joinedGroupResponse.groups;
-        dis.dispatch({
-            action: 'all_tags',
-            tags: joinedGroupIds,
-        });
-    },
-
     render() {
         const AccessibleButton = sdk.getComponent('elements.AccessibleButton');
         const TintableSvg = sdk.getComponent('elements.TintableSvg');