refactor: implement tenant self queue for rag tasks

api/core/entities/document_task.py

@@ -0,0 +1,13 @@
+from dataclasses import dataclass
+
+
+@dataclass
+class DocumentTask:
+    """Document task entity for document indexing operations.
+    
+    This class represents a document indexing task that can be queued
+    and processed by the document indexing system.
+    """
+    tenant_id: str
+    dataset_id: str
+    document_ids: list[str]