Django 2.0 will make this field required for `ForeignKey` and `OneToOneFields`.
In previous versions the option defaulted to `models.CASCADE` when not
specified. This change should make the deprecation warnings in the current
Django version go away.
The migrations where also modified, but the changes should not cause a change in
the database schema since `models.CASCADE` was already the old default.
As work progressed on entitlement support tool,
additional clarity around the entitlement support
detail fields was needed, this adds the action field
at a later point the reason field will be removed
Learner-3925
The Entitlement API will allow for GET, POST, DELETE(Revoke), and
variations of these methods of managing and retrieving data about
Learner Entitlements.
[LEARNER-2661]
