[MM-56986] imports/import_validators: add valid guest role check (#28658)

server/i18n/en.json

@@ -5730,6 +5730,10 @@
     "id": "app.import.validate_user_import_data.first_name_length.error",
     "translation": "User First Name is too long."
   },
+  {
+    "id": "app.import.validate_user_import_data.guest_roles_conflict.error",
+    "translation": "User roles are not consistent with guest status."
+  },
   {
     "id": "app.import.validate_user_import_data.last_name_length.error",
     "translation": "User Last Name is too long."