Add time utils (#10849)

### What problem does this PR solve?

- Add time utilities and unit tests

### Type of change

- [x] Refactoring

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Signed-off-by: Jin Hai <haijin.chn@gmail.com>

api/db/services/task_service.py

@@ -27,7 +27,8 @@ from api.db import StatusEnum, FileType, TaskStatus
 from api.db.db_models import Task, Document, Knowledgebase, Tenant
 from api.db.services.common_service import CommonService
 from api.db.services.document_service import DocumentService
-from api.utils import current_timestamp, get_uuid
+from api.utils import get_uuid
+from common.time_utils import current_timestamp
 from deepdoc.parser.excel_parser import RAGFlowExcelParser
 from rag.settings import get_svr_queue_name
 from rag.utils.storage_factory import STORAGE_IMPL