rails g migration AddIndexToMessages message_id_header:index

removing the generator added `add_column` line

Author: amatsuda

db/migrate/20251022024234_add_index_to_messages.rb

@@ -0,0 +1,5 @@
+class AddIndexToMessages < ActiveRecord::Migration[8.0]
+  def change
+    add_index :messages, :message_id_header
+  end
+end