add index on external id

db/migrate/20240624102526_add_index_on_external_id.rb

@@ -0,0 +1,8 @@
+# frozen_string_literal: true
+
+class AddIndexOnExternalId < ActiveRecord::Migration[7.1]
+  def change
+    add_index :submitters, :external_id
+    add_index :templates, :external_id
+  end
+end