MM-26057 - Add CreateCommand plugin API (#14916)

Automatic Merge

i18n/en.json

@@ -5594,6 +5594,10 @@
     "id": "model.command.is_valid.method.app_error",
     "translation": "Invalid Method."
   },
+  {
+    "id": "model.command.is_valid.plugin_id.app_error",
+    "translation": "Invalid plugin id."
+  },
   {
     "id": "model.command.is_valid.team_id.app_error",
     "translation": "Invalid team ID."