Add default ctor to PathItem

Signed-off-by: Matheus Cruz <matheuscruz.dev@gmail.com>

Author: mcruzdev

impl/openapi/src/main/java/io/serverlessworkflow/impl/executors/openapi/UnifiedOpenAPI.java

@@ -139,14 +139,16 @@ public record Server(String url) {}
 
   @JsonIgnoreProperties(ignoreUnknown = true)
   public static final class PathItem {
-    private final Operation get;
-    private final Operation post;
-    private final Operation put;
-    private final Operation delete;
-    private final Operation patch;
-    private final Operation head;
-    private final Operation options;
-    private final Set<HttpOperation> methods;
+    private Operation get;
+    private Operation post;
+    private Operation put;
+    private Operation delete;
+    private Operation patch;
+    private Operation head;
+    private Operation options;
+    private Set<HttpOperation> methods;
+
+    PathItem() {}
 
     public PathItem(
         Operation get,