Add Django core Redis backend

[Andrew-Chen-Wang]

Description

Django added the Redis backend to Django core.

Rationale

We already test the third party Redis backend. Some people are inclined to use the built-in one, so we should test it.
//: # (Why should this feature be implemented?)
//: # (Does it improve upon the software?)

Use case(s) / visualization(s)

Some people just want to use the Django core backend.

Alternatives?

The third party version
//: # (With every design comes another better or worse one)
//: # (We need to know all possible alternatives)