[MM-61691] Deleting drafts when permanently deleting a user (#30233)

* deleting drafts on permanently deleting user

* verified count of drafts before deleting

* i18n fix

* use ExecBuilder

* changed error message to specify user

---------

Co-authored-by: Mattermost Build <build@mattermost.com>
Co-authored-by: Harshil Sharma <harshilsharma63@gmail.com>

server/i18n/en.json

@@ -5122,6 +5122,10 @@
     "id": "app.draft.save.app_error",
     "translation": "Unable to save the Draft."
   },
+  {
+    "id": "app.drafts.permanent_delete_by_user.app_error",
+    "translation": "Unable to delete drafts for user."
+  },
   {
     "id": "app.email.no_rate_limiter.app_error",
     "translation": "Rate limiter is not set up."