Tutorial part 5 uses broken undocumented feature

[Baptiste Mispelon]

As reported in #20241, passing callable arguments to a queryset's filter method doesn't actually work the way it's described in the tutorial [1].

It's also an undocumented feature (#11629).

[1] ​https://github.com/django/django/blob/master/docs/intro/tutorial05.txt#L408-L411

[Baptiste Mispelon]

Here's a first attempt at rewriting the documentation: ​https://github.com/django/django/pull/1025

[Baptiste Mispelon]

After some comments from Jacob on IRC, I changed the approach and modified the pull request.

His concerns were that the added code was distracting the reader from the real purpose of that part of the tutorial (testing).

This new version changes the part 4 of the tutorial to make the changes introduced in the 5th part more seamless and less awkward.

For reference, I kept the older version on a different branch: ​https://github.com/bmispelon/django/compare/master...ticket-20249-backup.

[Tim Graham <timograham@…>]

In 679a2ac843567d32c95ccc46a215bc453ccfa2d0:

Fixed #20249 - Removed a "feature" in the tutorial that doesn't actually work.

Thanks bmispelon for the report and draft patch.

[Tim Graham <timograham@…>]

In 13de270bd52d057584023de08ea869722a7e5d5a:

[1.5.X] Fixed #20249 - Removed a "feature" in the tutorial that doesn't actually work.

Thanks bmispelon for the report and draft patch.

Backport of 679a2ac843 from master