PLT-6403: Interactive messages (#7274)

* wip

* finish first pass

* requested changes

* add DoPostAction to Client4

i18n/en.json

@@ -1759,6 +1759,14 @@
     "id": "api.post_get_post_by_id.get.app_error",
     "translation": "Unable to get post"
   },
+  {
+    "id": "api.post.do_action.action_id.app_error",
+    "translation": "Invalid action id"
+  },
+  {
+    "id": "api.post.do_action.action_integration.app_error",
+    "translation": "Action integration error"
+  },
   {
     "id": "api.preference.delete_preferences.decode.app_error",
     "translation": "Unable to decode preferences from request"