fix(migrations): Split add_column and index (#2276)

## Description

Add column first, then add index without transaction.

db/migrate/20240701184757_add_deleted_at_to_fees.rb

@@ -1,10 +1,7 @@
 # frozen_string_literal: true
 
 class AddDeletedAtToFees < ActiveRecord::Migration[7.1]
- disable_ddl_transaction!
-
  def change
  add_column :fees, :deleted_at, :datetime
- add_index :fees, :deleted_at, algorithm: :concurrently
  end
 end

db/migrate/20240711091155_add_fee_deleted_at_index.rb

@@ -0,0 +1,9 @@
+# frozen_string_literal: true
+
+class AddFeeDeletedAtIndex < ActiveRecord::Migration[7.1]
+ disable_ddl_transaction!
+
+ def change
+ add_index :fees, :deleted_at, algorithm: :concurrently, if_not_exists: true
+ end
+end