Added to the HTTP API test suite (#12556)

### What problem does this PR solve?

This PR adds missing HTTP API test coverage for dataset
graph/GraphRAG/RAPTOR tasks, metadata summary, chat completions, agent
sessions/completions, and related questions. It also introduces minimal
HTTP test helpers to exercise these endpoints consistently with the
existing suite.

### Type of change

- [x]  Other (please describe): Test coverage (HTTP API tests)

---------

Co-authored-by: Liu An <asiro@qq.com>

test/testcases/test_http_api/common.py

@@ -28,6 +28,8 @@ CHUNK_API_URL = f"/api/{VERSION}/datasets/{{dataset_id}}/documents/{{document_id
 CHAT_ASSISTANT_API_URL = f"/api/{VERSION}/chats"
 SESSION_WITH_CHAT_ASSISTANT_API_URL = f"/api/{VERSION}/chats/{{chat_id}}/sessions"
 SESSION_WITH_AGENT_API_URL = f"/api/{VERSION}/agents/{{agent_id}}/sessions"
+AGENT_API_URL = f"/api/{VERSION}/agents"
+RETRIEVAL_API_URL = f"/api/{VERSION}/retrieval"
 
 
 # DATASET MANAGEMENT
@@ -170,7 +172,7 @@ def delete_chunks(auth, dataset_id, document_id, payload=None):
 
 
 def retrieval_chunks(auth, payload=None):
-    url = f"{HOST_ADDRESS}/api/v1/retrieval"
+    url = f"{HOST_ADDRESS}{RETRIEVAL_API_URL}"
     res = requests.post(url=url, headers=HEADERS, auth=auth, json=payload)
     return res.json()
 
@@ -237,6 +239,8 @@ def update_session_with_chat_assistant(auth, chat_assistant_id, session_id, payl
 
 def delete_session_with_chat_assistants(auth, chat_assistant_id, payload=None):
     url = f"{HOST_ADDRESS}{SESSION_WITH_CHAT_ASSISTANT_API_URL}".format(chat_id=chat_assistant_id)
+    if payload is None:
+        payload = {}
     res = requests.delete(url=url, headers=HEADERS, auth=auth, json=payload)
     return res.json()
 
@@ -247,3 +251,107 @@ def batch_add_sessions_with_chat_assistant(auth, chat_assistant_id, num):
         res = create_session_with_chat_assistant(auth, chat_assistant_id, {"name": f"session_with_chat_assistant_{i}"})
         session_ids.append(res["data"]["id"])
     return session_ids
+
+
+# DATASET GRAPH AND TASKS
+def knowledge_graph(auth, dataset_id, params=None):
+    url = f"{HOST_ADDRESS}{DATASETS_API_URL}/{dataset_id}/knowledge_graph"
+    res = requests.get(url=url, headers=HEADERS, auth=auth, params=params)
+    return res.json()
+
+
+def delete_knowledge_graph(auth, dataset_id, payload=None):
+    url = f"{HOST_ADDRESS}{DATASETS_API_URL}/{dataset_id}/knowledge_graph"
+    if payload is None:
+        res = requests.delete(url=url, headers=HEADERS, auth=auth)
+    else:
+        res = requests.delete(url=url, headers=HEADERS, auth=auth, json=payload)
+    return res.json()
+
+
+def run_graphrag(auth, dataset_id, payload=None):
+    url = f"{HOST_ADDRESS}{DATASETS_API_URL}/{dataset_id}/run_graphrag"
+    res = requests.post(url=url, headers=HEADERS, auth=auth, json=payload)
+    return res.json()
+
+
+def trace_graphrag(auth, dataset_id, params=None):
+    url = f"{HOST_ADDRESS}{DATASETS_API_URL}/{dataset_id}/trace_graphrag"
+    res = requests.get(url=url, headers=HEADERS, auth=auth, params=params)
+    return res.json()
+
+
+def run_raptor(auth, dataset_id, payload=None):
+    url = f"{HOST_ADDRESS}{DATASETS_API_URL}/{dataset_id}/run_raptor"
+    res = requests.post(url=url, headers=HEADERS, auth=auth, json=payload)
+    return res.json()
+
+
+def trace_raptor(auth, dataset_id, params=None):
+    url = f"{HOST_ADDRESS}{DATASETS_API_URL}/{dataset_id}/trace_raptor"
+    res = requests.get(url=url, headers=HEADERS, auth=auth, params=params)
+    return res.json()
+
+
+def metadata_summary(auth, dataset_id, params=None):
+    url = f"{HOST_ADDRESS}{DATASETS_API_URL}/{dataset_id}/metadata/summary"
+    res = requests.get(url=url, headers=HEADERS, auth=auth, params=params)
+    return res.json()
+
+
+# CHAT COMPLETIONS AND RELATED QUESTIONS
+def chat_completions(auth, chat_assistant_id, payload=None):
+    url = f"{HOST_ADDRESS}{CHAT_ASSISTANT_API_URL}/{chat_assistant_id}/completions"
+    res = requests.post(url=url, headers=HEADERS, auth=auth, json=payload)
+    return res.json()
+
+
+def related_questions(auth, payload=None):
+    url = f"{HOST_ADDRESS}/api/{VERSION}/sessions/related_questions"
+    res = requests.post(url=url, headers=HEADERS, auth=auth, json=payload)
+    return res.json()
+
+
+# AGENT MANAGEMENT AND SESSIONS
+def create_agent(auth, payload=None):
+    url = f"{HOST_ADDRESS}{AGENT_API_URL}"
+    res = requests.post(url=url, headers=HEADERS, auth=auth, json=payload)
+    return res.json()
+
+
+def list_agents(auth, params=None):
+    url = f"{HOST_ADDRESS}{AGENT_API_URL}"
+    res = requests.get(url=url, headers=HEADERS, auth=auth, params=params)
+    return res.json()
+
+
+def delete_agent(auth, agent_id):
+    url = f"{HOST_ADDRESS}{AGENT_API_URL}/{agent_id}"
+    res = requests.delete(url=url, headers=HEADERS, auth=auth)
+    return res.json()
+
+
+def create_agent_session(auth, agent_id, payload=None, params=None):
+    url = f"{HOST_ADDRESS}{SESSION_WITH_AGENT_API_URL}".format(agent_id=agent_id)
+    res = requests.post(url=url, headers=HEADERS, auth=auth, json=payload, params=params)
+    return res.json()
+
+
+def list_agent_sessions(auth, agent_id, params=None):
+    url = f"{HOST_ADDRESS}{SESSION_WITH_AGENT_API_URL}".format(agent_id=agent_id)
+    res = requests.get(url=url, headers=HEADERS, auth=auth, params=params)
+    return res.json()
+
+
+def delete_agent_sessions(auth, agent_id, payload=None):
+    url = f"{HOST_ADDRESS}{SESSION_WITH_AGENT_API_URL}".format(agent_id=agent_id)
+    if payload is None:
+        payload = {}
+    res = requests.delete(url=url, headers=HEADERS, auth=auth, json=payload)
+    return res.json()
+
+
+def agent_completions(auth, agent_id, payload=None):
+    url = f"{HOST_ADDRESS}{AGENT_API_URL}/{agent_id}/completions"
+    res = requests.post(url=url, headers=HEADERS, auth=auth, json=payload)
+    return res.json()