Don't allow users to be added to a channel they are not in the team of (#3246)

i18n/en.json

@@ -3491,6 +3491,10 @@
     "id": "store.sql_team.get_by_name.app_error",
     "translation": "We couldn't find the existing team"
   },
+  {
+    "id": "store.sql_team.get_member.missing.app_error",
+    "translation": "No team member found for that user id and team id"
+  },
   {
     "id": "store.sql_team.get_member.app_error",
     "translation": "We couldn't get the team member"