Remove WeakForeignKey

[thomasfillon]

Commit ee63244073e19244714327d1adce57dc096b3d3c add weakforeignkey in to "emulate sql ON DELETE SET NULL using WeakForeignKey and enhanced model/manager/queryset"

See models.fields.py line 202

This feature seems obsolete as it is provided by Django. see https://docs.djangoproject.com/en/1.8/ref/models/fields/#django.db.models.ForeignKey.on_delete

For example, if you have a nullable ForeignKey and you want it to be set null when the referenced object is deleted:

user = models.ForeignKey(User, blank=True, null=True, on_delete=models.SET_NULL)

Todo :

• remove WeakForeignKey class
• modifiy every models using WeakForeignKey by adding the option on_delete=models.SET_NULL.
• EnhancedQuerySet, EnhancedManager, and EnhancedModel in models.core.py may also not be needed any more.

@yomguy do you confirm that EnhancedQuerySet, EnhancedManager, and EnhancedModel could be removed ? EnhancedModel is used as base-class for ModelCore but seems only to add weakforeignkey support. Is it wright ?

[thomasfillon]

notes:

• 179 may be related to this issue for Django >= 1.8

• commit ee63244 that introduced WeakForeignKey also provide unit tests to test the "on delete set null" behavior.

[thomasfillon]

See Django documentation on Migrations: Considerations when removing model fields

[thomasfillon]

Fix with #186 in release/1.7