Custom manager that excludes soft deleted records by default

[kelvin-muchiri]

Suggested Feature / Enhancement

When making queries, soft deleted items are included in the queryset unless explicitly filtered out e.g deleted_at__isnull=True. It is easy to forget to exclude soft deleted records. The side effect is accidental exposure of deleted records when returning API responses.

We should use a custom manager that excludes soft deleted items by default, but also provides an API for getting all records including soft deleted items.

Benefits of implementing the feature/enhancement

Prevents accidental exposure of soft deleted items.

Suggested implementation plan(Steps to be taken to implement feature)

1. Create a custom queryset with methods to exclude soft-deleted records and to include all records.

class SoftDeleteQuerySet(models.QuerySet):
    def active(self):
        return self.filter(deleted_at__isnull=True)

    def all_with_deleted(self):
        return self

2. Create a custom manager that makes use of the custom queryset

class SoftDeleteManager(models.Manager):
    def get_queryset(self):
        return SoftDeleteQuerySet(self.model, using=self._db).active()

    def all_with_deleted(self):
        return self.get_queryset().all_with_deleted()

3. Update models to use the custom manager

class MyModel(models.Model):
    ...
    deleted_at = models.DateTimeField(null=True, blank=True)
    ...

    objects = SoftDeleteManager()

4. To get active records

active_records = MyModel.objects.all()

5. To get all records including soft deleted items

all_records = MyModel.objects.all_with_deleted()

[ukanga]

Should this be added to our BaseModel? Which adds the other required fields.