Feat: Add knowledge graph http api (#8896)

### What problem does this PR solve?

Add knowledge graph http api

### Type of change

- [x] New Feature (non-breaking change which adds functionality)

api/apps/sdk/dataset.py

 
 import logging
 import os
+import json
 
 from flask import request
 from peewee import OperationalError
     except OperationalError as e:
         logging.exception(e)
         return get_error_data_result(message="Database operation failed")
+
+@manager.route('/datasets/<dataset_id>/knowledge_graph', methods=['GET'])  # noqa: F821
+@token_required
+def knowledge_graph(tenant_id,dataset_id):
+    if not KnowledgebaseService.accessible(dataset_id, tenant_id):
+        return get_result(
+            data=False,
+            message='No authorization.',
+            code=settings.RetCode.AUTHENTICATION_ERROR
+        )
+    _, kb = KnowledgebaseService.get_by_id(dataset_id)
+    req = {
+        "kb_id": [dataset_id],
+        "knowledge_graph_kwd": ["graph"]
+    }
+
+    obj = {"graph": {}, "mind_map": {}}
+    if not settings.docStoreConn.indexExist(search.index_name(kb.tenant_id), dataset_id):
+        return get_result(data=obj)
+    sres = settings.retrievaler.search(req, search.index_name(kb.tenant_id), [dataset_id])
+    if not len(sres.ids):
+        return get_result(data=obj)
+
+    for id in sres.ids[:1]:
+        ty = sres.field[id]["knowledge_graph_kwd"]
+        try:
+            content_json = json.loads(sres.field[id]["content_with_weight"])
+        except Exception:
+            continue
+
+        obj[ty] = content_json
+
+    if "nodes" in obj["graph"]:
+        obj["graph"]["nodes"] = sorted(obj["graph"]["nodes"], key=lambda x: x.get("pagerank", 0), reverse=True)[:256]
+        if "edges" in obj["graph"]:
+            node_id_set = { o["id"] for o in obj["graph"]["nodes"] }
+            filtered_edges = [o for o in obj["graph"]["edges"] if o["source"] != o["target"] and o["source"] in node_id_set and o["target"] in node_id_set]
+            obj["graph"]["edges"] = sorted(filtered_edges, key=lambda x: x.get("weight", 0), reverse=True)[:128]
+    return get_result(data=obj)
+
+@manager.route('/datasets/<dataset_id>/knowledge_graph', methods=['DELETE'])  # noqa: F821
+@token_required
+def delete_knowledge_graph(tenant_id,dataset_id):
+    if not KnowledgebaseService.accessible(dataset_id, tenant_id):
+        return get_result(
+            data=False,
+            message='No authorization.',
+            code=settings.RetCode.AUTHENTICATION_ERROR
+        )
+    _, kb = KnowledgebaseService.get_by_id(dataset_id)
+    settings.docStoreConn.delete({"knowledge_graph_kwd": ["graph", "subgraph", "entity", "relation"]}, search.index_name(kb.tenant_id), dataset_id)
+
+    return get_result(data=True)

docs/references/http_api_reference.md

     "message": "The dataset doesn't exist"
 }
 ```
+ ---
 
+## Get dataset's knowledge graph
+
+**GET** `/api/v1/datasets/{dataset_id}/knowledge_graph`
+
+Gets the knowledge graph of a specific datasets.
+
+#### Request
+
+- Method: GET
+- URL: `/api/v1/datasets/{dataset_id}/knowledge_graph`
+- Headers:
+  - `'Authorization: Bearer <YOUR_API_KEY>'`
+
+##### Request example
+
+```bash
+curl --request GET \
+     --url http://{address}/api/v1/datasets/{dataset_id}/knowledge_graph \
+     --header 'Authorization: Bearer <YOUR_API_KEY>'
+```
+
+##### Request parameters
+
+- `dataset_id`: (*Path parameter*)  
+  The ID of the dataset.
+
+#### Response
+
+Success:
+
+```json
+{
+    "code": 0,
+    "data": {
+        "graph": {
+            "directed": false,
+            "edges": [
+                {
+                    "description": "The notice is a document issued to convey risk warnings and operational alerts.<SEP>The notice is a specific instance of a notification document issued under the risk warning framework.",
+                    "keywords": ["9", "8"],
+                    "source": "notice",
+                    "source_id": ["8a46cdfe4b5c11f0a5281a58e595aa1c"],
+                    "src_id": "xxx",
+                    "target": "xxx",
+                    "tgt_id": "xxx",
+                    "weight": 17.0
+                }
+            ],
+            "graph": {
+                "source_id": ["8a46cdfe4b5c11f0a5281a58e595aa1c", "8a7eb6424b5c11f0a5281a58e595aa1c"]
+            },
+            "multigraph": false,
+            "nodes": [
+                {
+                    "description": "xxx",
+                    "entity_name": "xxx",
+                    "entity_type": "ORGANIZATION",
+                    "id": "xxx",
+                    "pagerank": 0.10804906590624092,
+                    "rank": 3,
+                    "source_id": ["8a7eb6424b5c11f0a5281a58e595aa1c"]
+                }
+            ]
+        },
+        "mind_map": {}
+    }
+}
+```
+
+Failure:
+
+```json
+{
+    "code": 102,
+    "message": "The dataset doesn't exist"
+}
+```
+---
+
+## Delete dataset's knowledge graph
+
+**DELETE** `/api/v1/datasets/{dataset_id}/knowledge_graph`
+
+Deletes the knowledge graph of a specific datasets.
+
+#### Request
+
+- Method: DELETE
+- URL: `/api/v1/datasets/{dataset_id}/knowledge_graph`
+- Headers:
+  - `'Authorization: Bearer <YOUR_API_KEY>'`
+
+##### Request example
+
+```bash
+curl --request DELETE \
+     --url http://{address}/api/v1/datasets/{dataset_id}/knowledge_graph \
+     --header 'Authorization: Bearer <YOUR_API_KEY>'
+```
+
+##### Request parameters
+
+- `dataset_id`: (*Path parameter*)  
+  The ID of the dataset.
+
+#### Response
+
+Success:
+
+```json
+{
+    "code": 0,
+    "data": true
+}
+```
+
+Failure:
+
+```json
+{
+    "code": 102,
+    "message": "The dataset doesn't exist"
+}
+```
 ---
 
 ## FILE MANAGEMENT WITHIN DATASET