Add a migration feature

inc/Config/DataSource/HttpDataSource.php

@@ -44,6 +44,8 @@ final public function get_service_name(): string {
 	 * define their own validation schema.
 	 */
 	public static function preprocess_config( array $config ): array|WP_Error {
+		$config = static::perform_migration( $config );
+
 		$service_config = $config['service_config'] ?? [];
 		$validator = new Validator( static::get_service_config_schema() );
 		$validated = $validator->validate( $service_config );
@@ -63,6 +65,31 @@ public static function preprocess_config( array $config ): array|WP_Error {
 		);
 	}
 
+	/**
+	 * Performs a migration if the config is out of date.
+	 */
+	private static function perform_migration( array $config ): array {
+		// By default, we want to have an active data source.
+		if ( ! isset( $config['active'] ) ) {
+			$config['active'] = true;
+		}
+
+		if ( static::SERVICE_SCHEMA_VERSION === $config['service_config']['__version'] ) {
+			return $config;
+		}
+
+		$migrated_config = static::migrate_config( $config );
+
+		if ( is_wp_error( $migrated_config ) ) {
+			$config['active'] = false;
+		} else {
+			$config['service_config']['__version'] = static::SERVICE_SCHEMA_VERSION;
+			$config['active'] = true;
+		}
+
+		return $config;
+	}
+
 	public static function from_uuid( string $uuid ): DataSourceInterface|WP_Error {
 		$config = DataSourceCrud::get_config_by_uuid( $uuid );
 
@@ -105,4 +132,12 @@ protected static function map_service_config( array $service_config ): array {
 			'request_headers' => $service_config['request_headers'] ?? [],
 		];
 	}
+
+	/**
+	 * Migrates the config to the current schema version.
+	 * Can be overridden by child classes to perform custom migrations.
+	 */
+	protected static function migrate_config( array $config ): array {
+		return $config;
+	}
 }