fix: HTTP+JSON transport returns 501 instead of 400 for UnsupportedOperationError.

Returning the proper satuts code.

Signed-off-by: Emmanuel Hugonnet <ehugonne@redhat.com>

Author: ehsavoie

transport/rest/src/main/java/io/a2a/transport/rest/handler/RestHandler.java

@@ -764,33 +764,42 @@ private static int mapErrorToHttpStatus(A2AError error) {
             return errorCode.httpCode();
         }
         if (error instanceof InvalidParamsError) {
-            return 422;
+            return A2AErrorCodes.INVALID_PARAMS.httpCode();
         }
-        if (error instanceof MethodNotFoundError || error instanceof TaskNotFoundError) {
-            return 404;
+        if (error instanceof MethodNotFoundError) {
+            return A2AErrorCodes.METHOD_NOT_FOUND.httpCode();
+        }
+        if (error instanceof TaskNotFoundError) {
+            return A2AErrorCodes.TASK_NOT_FOUND.httpCode();
         }
         if (error instanceof TaskNotCancelableError) {
-            return 409;
+            return A2AErrorCodes.TASK_NOT_CANCELABLE.httpCode();
         }
         if (error instanceof UnsupportedOperationError) {
-            return 501;
+            return A2AErrorCodes.UNSUPPORTED_OPERATION.httpCode();
         }
         if (error instanceof ContentTypeNotSupportedError) {
-            return 415;
+            return A2AErrorCodes.CONTENT_TYPE_NOT_SUPPORTED.httpCode();
         }
         if (error instanceof InvalidAgentResponseError) {
-            return 502;
+            return A2AErrorCodes.INVALID_AGENT_RESPONSE.httpCode();
+        }
+        if (error instanceof ExtendedAgentCardNotConfiguredError) {
+            return A2AErrorCodes.EXTENDED_AGENT_CARD_NOT_CONFIGURED.httpCode();
+        }
+        if (error instanceof ExtensionSupportRequiredError) {
+            return A2AErrorCodes.EXTENSION_SUPPORT_REQUIRED.httpCode();
+        }
+        if (error instanceof VersionNotSupportedError) {
+            return A2AErrorCodes.VERSION_NOT_SUPPORTED.httpCode();
         }
-        if (error instanceof ExtendedAgentCardNotConfiguredError
-                || error instanceof ExtensionSupportRequiredError
-                || error instanceof VersionNotSupportedError
-                || error instanceof PushNotificationNotSupportedError) {
-            return 400;
+        if (error instanceof PushNotificationNotSupportedError) {
+            return A2AErrorCodes.PUSH_NOTIFICATION_NOT_SUPPORTED.httpCode();
         }
         if (error instanceof InternalError) {
-            return 500;
+            return A2AErrorCodes.INTERNAL.httpCode();
         }
-        return 500;
+        return A2AErrorCodes.INTERNAL.httpCode();
     }
 
     /**