Add Migration for address change identifiers

Add a migration as a followup for commit 82fbafd

In that commit  we changed how we store the address change identifiers
and made the columns non-nullable, but forgot to migrate old address
change entries where the `previous_identifier` defaulted to NULL.

Author: gbirke

src/DataAccess/Migrations/Version20241113164504.php

@@ -0,0 +1,32 @@
+<?php
+
+declare( strict_types=1 );
+
+namespace WMDE\Fundraising\AddressChangeContext\DataAccess\Migrations;
+
+use Doctrine\DBAL\Schema\Schema;
+use Doctrine\Migrations\AbstractMigration;
+
+/**
+ * This migration is a followup for commit 82fbafd0df529ba9604b35ef805174d1a4c390fa
+ * where we changed how we store the address change identifiers and made the columns non-nullable,
+ * but forgot to migrate old address change entries where the `previous_identifier` defaulted to NULL.
+ */
+final class Version20241113164504 extends AbstractMigration {
+	public function getDescription(): string {
+		return 'Make address change identifiers non-nullable';
+	}
+
+	public function up( Schema $schema ): void {
+		$this->addSql( "UPDATE address_change SET previous_identifier=current_identifier WHERE previous_identifier IS NULL AND current_identifier IS NOT NULL" );
+		// We can't use $schema here to modify the columns because `addSQL` appends to the SQL generated by $schema calls.
+		// We would fail the migration when trying to set a column to non-nullable if it already contains NULL values
+		$this->addSql( "ALTER TABLE address_change MODIFY current_identifier VARCHAR(36) NOT NULL, MODIFY previous_identifier VARCHAR(36) NOT NULL " );
+	}
+
+	public function down( Schema $schema ): void {
+		$addressChange = $schema->getTable( 'address_change' );
+		$addressChange->modifyColumn( 'current_identifier', [ 'notnull' => false ] );
+		$addressChange->modifyColumn( 'previous_identifier', [ 'notnull' => false ] );
+	}
+}