PLT-6023: Add Users to Team in WebApp. (#5956)

* PLT-6198: Use added to channel system message on default channels.

Use a different sytem message when a user was added to a default channel
by someone else than when they joined themselves.

* PLT-6023: Add Users to Team in WebApp.

* Fix string text.

* Handle added_to_team websocket message.

* Fix unread flag on new channel.

webapp/utils/constants.jsx

@@ -95,6 +95,7 @@ export const ActionTypes = keyMirror({
 
     RECEIVED_PROFILES: null,
     RECEIVED_PROFILES_IN_TEAM: null,
+    RECEIVED_PROFILES_NOT_IN_TEAM: null,
     RECEIVED_PROFILE: null,
     RECEIVED_PROFILES_IN_CHANNEL: null,
     RECEIVED_PROFILES_NOT_IN_CHANNEL: null,
@@ -137,6 +138,7 @@ export const ActionTypes = keyMirror({
 
     RECEIVED_MSG: null,
 
+    RECEIVED_TEAM: null,
     RECEIVED_MY_TEAM: null,
     CREATED_TEAM: null,
     UPDATE_TEAM: null,
@@ -219,6 +221,7 @@ export const SocketEvents = {
     CHANNEL_VIEWED: 'channel_viewed',
     DIRECT_ADDED: 'direct_added',
     NEW_USER: 'new_user',
+    ADDED_TO_TEAM: 'added_to_team',
     LEAVE_TEAM: 'leave_team',
     UPDATE_TEAM: 'update_team',
     USER_ADDED: 'user_added',