Pipeline task management

Session persists a collection of tasks with unique identifiers; shared pipeline caller can optionally enqueue its call as a task instead of running it directly

model_server/base/pipelines/shared.py

@@ -53,7 +53,7 @@ def call_pipeline(func, p: PipelineParams) -> Union[PipelineRecord, PipelineQueu
     # instead of running right away, schedule pipeline as a task
     if p.schedule:
         p.schedule = False
-        task_id = session.queue.add_task(
+        task_id = session.tasks.add_task(
             lambda x: call_pipeline(func, x),
             p
         )