Test: Add dialog app test suite and update common.py with dialog endpoints (#8729)

### What problem does this PR solve?

This commit introduces a comprehensive test suite for the dialog app,
including tests for creating, updating, retrieving, listing, and
deleting dialogs. Additionally, the common.py file has been updated to
include necessary API endpoints and helper functions for dialog
operations.

### Type of change

- [x] Add test cases

test/testcases/test_web_api/test_dialog_app/conftest.py

@@ -0,0 +1,50 @@
+#
+#  Copyright 2025 The InfiniFlow Authors. All Rights Reserved.
+#
+#  Licensed under the Apache License, Version 2.0 (the "License");
+#  you may not use this file except in compliance with the License.
+#  You may obtain a copy of the License at
+#
+#      http://www.apache.org/licenses/LICENSE-2.0
+#
+#  Unless required by applicable law or agreed to in writing, software
+#  distributed under the License is distributed on an "AS IS" BASIS,
+#  WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+#  See the License for the specific language governing permissions and
+#  limitations under the License.
+#
+import pytest
+from common import batch_create_dialogs, delete_dialogs
+
+
+@pytest.fixture(scope="function")
+def add_dialog_func(request, WebApiAuth, add_dataset_func):
+    def cleanup():
+        delete_dialogs(WebApiAuth)
+
+    request.addfinalizer(cleanup)
+
+    dataset_id = add_dataset_func
+    return dataset_id, batch_create_dialogs(WebApiAuth, 1, [dataset_id])[0]
+
+
+@pytest.fixture(scope="class")
+def add_dialogs(request, WebApiAuth, add_dataset):
+    def cleanup():
+        delete_dialogs(WebApiAuth)
+
+    request.addfinalizer(cleanup)
+
+    dataset_id = add_dataset
+    return dataset_id, batch_create_dialogs(WebApiAuth, 5, [dataset_id])
+
+
+@pytest.fixture(scope="function")
+def add_dialogs_func(request, WebApiAuth, add_dataset_func):
+    def cleanup():
+        delete_dialogs(WebApiAuth)
+
+    request.addfinalizer(cleanup)
+
+    dataset_id = add_dataset_func
+    return dataset_id, batch_create_dialogs(WebApiAuth, 5, [dataset_id])