fix: preserve serialized object payloads

src/Url/MetadataUrlTransformer.php

@@ -32,7 +32,7 @@ final class MetadataUrlTransformer {
 		if ( $this->looksSerialized( $value ) ) {
 			$unserialized = $this->unserializeValue( $value );
 
-			if ( ! $unserialized['valid'] || is_object( $unserialized['value'] ) ) {
+			if ( ! $unserialized['valid'] || $this->containsObject( $unserialized['value'] ) ) {
 				return $value;
 			}
 
@@ -118,4 +118,25 @@ final class MetadataUrlTransformer {
 
 		return '' !== $trimmed && in_array( $trimmed[0], array( '{', '[' ), true );
 	}
+
+	/**
+	 * @param mixed $value Value to inspect.
+	 */
+	private function containsObject( $value ): bool {
+		if ( is_object( $value ) ) {
+			return true;
+		}
+
+		if ( ! is_array( $value ) ) {
+			return false;
+		}
+
+		foreach ( $value as $item ) {
+			if ( $this->containsObject( $item ) ) {
+				return true;
+			}
+		}
+
+		return false;
+	}
 }