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/utils/constants.jsx

@@ -35,6 +35,7 @@ import windows10ThemeImage from 'images/themes/windows_dark.png';
 
 export const Preferences = {
     CATEGORY_DIRECT_CHANNEL_SHOW: 'direct_channel_show',
+    CATEGORY_GROUP_CHANNEL_SHOW: 'group_channel_show',
     CATEGORY_DISPLAY_SETTINGS: 'display_settings',
     DISPLAY_PREFER_NICKNAME: 'nickname_full_name',
     DISPLAY_PREFER_FULL_NAME: 'full_name',
@@ -164,6 +165,7 @@ export const ActionTypes = keyMirror({
     TOGGLE_GET_POST_LINK_MODAL: null,
     TOGGLE_GET_TEAM_INVITE_LINK_MODAL: null,
     TOGGLE_GET_PUBLIC_LINK_MODAL: null,
+    TOGGLE_DM_MODAL: null,
 
     SUGGESTION_PRETEXT_CHANGED: null,
     SUGGESTION_RECEIVED_SUGGESTIONS: null,
@@ -390,8 +392,11 @@ export const Constants = {
     ],
     MONTHS: ['January', 'February', 'March', 'April', 'May', 'June', 'July', 'August', 'September', 'October', 'November', 'December'],
     MAX_DMS: 20,
+    MAX_USERS_IN_GM: 8,
+    MIN_USERS_IN_GM: 3,
     MAX_CHANNEL_POPOVER_COUNT: 100,
     DM_CHANNEL: 'D',
+    GM_CHANNEL: 'G',
     OPEN_CHANNEL: 'O',
     PRIVATE_CHANNEL: 'P',
     INVITE_TEAM: 'I',