Delay task

This wait task completes after its delay_until timestamp.

The task_data for this task may contain the following keys:

• delay_until (datetime, required): a timestamp on or after which this task may be run

The workflow_data for this task contains needs_input: False.

As with other wait tasks, the scheduler marks it running (without assigning a worker) as soon as possible after it is pending, after which it is considered to be waiting for its event to happen. Separately, it handles the completion of this particular task directly, by marking it as successfully completed if the current time is greater than or equal to its delay_until timestamp.