Check directionality of job/route `on_delete` `CASCADE`

[thomaszwagerman]

Check that the directionality of the CASCADE behaviour is correct.

When Route is deleted, Job is deleted.

Is Route deleted, when Job is deleted?

class Route(models.Model):
    requested = models.DateTimeField(default=timezone.now)
    calculated = models.DateTimeField(null=True)
    info = models.JSONField(null=True)
    mesh = models.ForeignKey(Mesh, on_delete=models.SET_NULL, null=True)
    start_lat = models.FloatField()
    start_lon = models.FloatField()
    end_lat = models.FloatField()
    end_lon = models.FloatField()
    start_name = models.CharField(max_length=100, null=True, blank=True, default=None)
    end_name = models.CharField(max_length=100, null=True, blank=True, default=None)
    json = models.JSONField(null=True)
    json_unsmoothed = models.JSONField(null=True)
    polar_route_version = models.CharField(max_length=60, null=True)
    tags = TaggableManager(blank=True, help_text="Tags for route")


class Job(models.Model):
    "Route or mesh calculation jobs"

    id = models.UUIDField(
        primary_key=True
    )  # use uuids for primary keys to align with celery

    datetime = models.DateTimeField(default=timezone.now)
    route = models.ForeignKey(Route, on_delete=models.CASCADE)

    @property
    def status(self):
        result = AsyncResult(self.id, app=app)
        return result.state

Depends also on the relationship between routes and jobs. For example, when a route recalculated, with a different job, does the route retain its id or is a new route created?