Add django.contrib.redirects setting for turning redirect on/off.

[Lebedev Ilya]

At the moment django.contrib.redirects doesn't allow to disable particular redirect.
To do this I have do remove it completely or rename old_path to nonexistent. It neither clear nor correct.
Good solution is to add is_active bool field with default=True.

[Russell Keith-Magee]

A reasonable idea, but we're hampered by the lack of a built in schema migration system.

Marking it someday/maybe; once we have a built-in migration system, this sort of change will be easy to make, but in the meantime, it's a non-trivial change.

[ZeevG]

Can I assume this feature can be added now that we do have a built-in migration system?

I'm happy to write a patch, it seems like it might be a good ticket for me to get started with.

[Tim Graham]

@ZeevG, migrations is still under active development and I don't think we're quite ready to add them to contrib apps yet. Stay tuned.

[Aymeric Augustin]

The current plan is to make changes to models in contrib apps in Django 1.8.

[Tim Graham]

We'd need to include a documentation warning that since the default RedirectFallbackMiddleware.response_redirect_class is HttpResponsePermanentRedirect, the flag may have no effect on users who have already accessed the redirect and have it cached by their browser.

[Berker Peksag]

Pull request: ​https://github.com/django/django/pull/5137

[Tim Graham]

Discussion on the pull request with Berker concluded that adding this feature would likely be too confusing due to the default redirect being "permanent".