770 tree manager allow to specify desired task_type no prompter ranking (#775)

* only ranking assistant replies by default

* add tasks/availability endpoint allow to specify desired task

* move rank_prompter_replies option to TreeManagerConfiguration

* fix type annotation

* remove desired_task_type from _random_task_selection()

* fix typo

* Convert query_tree_size to sqlachemy, return 'full' text-labeling tasks if they were explicitly requested

backend/oasst_backend/api/v1/tasks.py

@@ -1,4 +1,4 @@
-from typing import Any
+from typing import Any, Optional
 from uuid import UUID
 
 from fastapi import APIRouter, Depends
@@ -48,6 +48,27 @@ def request_task(
     return task
 
 
+@router.post("/availability", response_model=dict[protocol_schema.TaskRequestType, int])
+def tasks_availability(
+    *,
+    user: Optional[protocol_schema.User] = None,
+    db: Session = Depends(deps.get_db),
+    api_key: APIKey = Depends(deps.get_api_key),
+):
+    api_client = deps.api_auth(api_key, db)
+
+    try:
+        pr = PromptRepository(db, api_client, client_user=user)
+        tm = TreeManager(db, pr)
+        return tm.determine_task_availability()
+
+    except OasstError:
+        raise
+    except Exception:
+        logger.exception("Task availability query failed.")
+        raise OasstError("Task availability query failed.", OasstErrorCode.TASK_AVAILABILITY_QUERY_FAILED)
+
+
 @router.post("/{task_id}/ack", response_model=None, status_code=HTTP_204_NO_CONTENT)
 def tasks_acknowledge(
     *,