WorkerRun and Task TTL

https://redmine.teklia.com/issues/8785

Requires #1870 (closed)

Two new database fields are added to manage the maximum execution time of a Ponos task:

• Task.ttl, the TTL of a single task. Non-negative integer representing seconds. Zero means infinite.
• WorkerRun.ttl, the TTL that will be passed on to all tasks created from this WorkerRun. Same definition as Task.ttl.

ListWorkerRuns and RetrieveWorkerRun should include WorkerRun.ttl in the API response.

CreateWorkerRun, PartialUpdateWorkerRun and UpdateWorkerRun allow setting the ttl. The maximum value for ttl is set to Corpus.maximum_task_ttl from the corpus of the process. If Corpus.maximum_task_ttl is None, to settings.PONOS_MAXIMUM_TASK_TTL. The default value when none is sent in CreateWorkerRun or UpdateWorkerRun is the maximum value.

RetrieveTask should include Task.ttl in the API response. It should not be editable through UpdateTask or PartialUpdateTask.

RetrieveProcess should include Task.ttl in the tasks in its response.

When creating a task, the ProcessBuilder should set the Task.ttl to the value of WorkerRun.ttl.

RestartTask should clone the Task.ttl of the original task.

CreateProcessTemplate should copy the TTL of the original WorkerRuns regardless of the limits. ApplyProcessTemplate should apply the limits according to the corpus of the destination process.

It should be possible to edit the value of both of these fields in the Django admin. The maximums enforced in the WorkerRun APIs are not enforced in the admin, to allow instance admins to override the limits in special cases.