fix completed submitters

db/migrate/20241026161207_add_unique_index_on_completed_submitters.rb

@@ -0,0 +1,8 @@
+# frozen_string_literal: true
+
+class AddUniqueIndexOnCompletedSubmitters < ActiveRecord::Migration[7.2]
+  def change
+    remove_index :completed_submitters, :submitter_id
+    add_index :completed_submitters, :submitter_id, unique: true
+  end
+end