Unified user_service.py (#4606)

### What problem does this PR solve?

Unified user_service.py

### Type of change

- [x] Refactoring

api/db/services/user_service.py

 #  See the License for the specific language governing permissions and
 #  limitations under the License.
 #
+import hashlib
 from datetime import datetime
 
 import peewee
 from api.db.services.common_service import CommonService
 from api.utils import get_uuid, current_timestamp, datetime_format
 from api.db import StatusEnum
+from rag.settings import MINIO
 
 
 class UserService(CommonService):
         else:
             return None
 
+    @classmethod
+    @DB.connection_context()
+    def user_gateway(cls, tenant_id):
+        hashobj = hashlib.sha256(tenant_id.encode("utf-8"))
+        return int(hashobj.hexdigest(), 16)%len(MINIO)
+
     @classmethod
     @DB.connection_context()
     def save(cls, **kwargs):