PLT-3077 Add group messaging (#5489)

* Implement server changes for group messaging

* Majority of client-side implementation

* Some server updates

* Added new React multiselect component

* Fix style issues

* Add custom renderer for options

* Fix model test

* Update ENTER functionality for multiselect control

* Remove buttons from multiselect UI control

* Updating group messaging UI (#5524)

* Move filter controls up a component level

* Scroll with arrow keys

* Updating mobile layout for multiselect (#5534)

* Fix race condition when backspacing quickly

* Hidden or new GMs show up for regular messages

* Add overriding of number remaining text

* Add UI filtering for team if config setting set

* Add icon to channel switcher and class prop to status icon

* Minor updates per feedback

* Improving group messaging UI (#5563)

* UX changes per feedback

* Update email for group messages

* UI fixes for group messaging (#5587)

* Fix missing localization string

* Add maximum users message when adding members to GM

* Fix input clearing on Android

* Updating group messaging UI (#5603)

* Updating UI for group messaging (#5604)

webapp/tests/client_channel.test.jsx

@@ -48,6 +48,37 @@ describe('Client.Channels', function() {
         });
     });
 
+    it('createGroupChannel', function(done) {
+        TestHelper.initBasic(() => {
+            TestHelper.basicClient().createUser(
+                TestHelper.fakeUser(),
+                (user1) => {
+                    TestHelper.basicClient().createUser(
+                        TestHelper.fakeUser(),
+                        function(user2) {
+                            TestHelper.basicClient().createGroupChannel(
+                                [user2.id, user1.id],
+                                function(data) {
+                                    assert.equal(data.id.length > 0, true);
+                                    done();
+                                },
+                                function(err) {
+                                    done(new Error(err.message));
+                                }
+                            );
+                        },
+                        function(err) {
+                            done(new Error(err.message));
+                        }
+                    );
+                },
+                function(err) {
+                    done(new Error(err.message));
+                }
+            );
+        });
+    });
+
     it('updateChannel', function(done) {
         TestHelper.initBasic(() => {
             var channel = TestHelper.basicChannel();