Model for storing the result and status of a task.
Note Only used if you’re running the database backend.
- 
task_id
 
- The unique task id.
 
- 
status
 
- The current status for this task.
 
- 
result
 
- The result after successful/failed execution. If the task failed,
this contains the execption it raised.
 
- 
date_done
 
- The date this task changed status.