Add a migration feature

inc/Config/ArraySerializable.php

@@ -34,6 +34,11 @@ final public static function from_array( array $config, ?ValidatorInterface $val
 			return $subclass::from_array( $config, $validator );
 		}
 
+		$config = static::migrate_config( $config );
+		if ( is_wp_error( $config ) ) {
+			return $config;
+		}
+
 		$config = static::preprocess_config( $config );
 		if ( is_wp_error( $config ) ) {
 			return $config;
@@ -91,4 +96,15 @@ protected static function get_implementor( array $config ): ?string {
 	 * @inheritDoc
 	 */
 	abstract public static function get_config_schema(): array;
+
+	/**
+	 * Migrates the config to the current schema version.
+	 * Can be overridden by child classes to perform custom migrations.
+	 *
+	 * @param array<string, mixed> $config The config to migrate.
+	 * @return array<string, mixed> The migrated config.
+	 */
+	public static function migrate_config( array $config ): array|WP_Error {
+		return $config;
+	}
 }

inc/Config/ArraySerializableInterface.php

@@ -39,6 +39,14 @@ public static function preprocess_config( array $config ): array|WP_Error;
 	 */
 	public static function get_config_schema(): array;
 
+	/**
+	 * Migrates the config to the current schema version.
+	 *
+	 * @param array<string, mixed> $config The config to migrate.
+	 * @return array<string, mixed> The migrated config.
+	 */
+	public static function migrate_config( array $config ): array|WP_Error;
+
 	/**
 	 * Converts the current object to an array representation.
 	 *

inc/Config/DataSource/HttpDataSource.php

@@ -105,4 +105,11 @@ protected static function map_service_config( array $service_config ): array {
 			'request_headers' => $service_config['request_headers'] ?? [],
 		];
 	}
+
+	/**
+	 * @inheritDoc
+	 */
+	public static function migrate_config( array $config ): array|WP_Error {
+		return $config;
+	}
 }