feat: add seekdb which is lite version of oceanbase (#12692)

### What problem does this PR solve?

Add seekdb as doc_engine wich is the lite version of oceanbase.
close #12691
### Type of change

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

docker/service_conf.yaml.template

@@ -38,6 +38,14 @@ oceanbase:
     password: '${OCEANBASE_PASSWORD:-infini_rag_flow}'
     host: '${OCEANBASE_HOST:-oceanbase}'
     port: ${OCEANBASE_PORT:-2881}
+seekdb:
+  scheme: 'oceanbase' # SeekDB is the lite version of OceanBase
+  config:
+    db_name: '${SEEKDB_DOC_DBNAME:-ragflow_doc}'
+    user: '${SEEKDB_USER:-root}'
+    password: '${SEEKDB_PASSWORD:-infini_rag_flow}'
+    host: '${SEEKDB_HOST:-seekdb}'
+    port: ${SEEKDB_PORT:-2881}
 redis:
   db: 1
   username: '${REDIS_USERNAME:-}'