Add filter().get_or_create() chaining to documentation to explain how to use get_or_create with Q objects

[Mike Lissner]

This technique is useful if you want to use Q objects in conjunction with the get or create method, and it's documented in a few places around the web.

I brought this up in the forums yesterday and somebody suggested that it be documented:

​https://groups.google.com/forum/?utm_medium=email&utm_source=footer#!msg/django-developers/e3sJ6OiHEd0/Yrg-Z9uRAgAJ

I gave this a try, but I don't understand the documentation system and I sadly don't have time to figure it out. Seems though like a change could go here:

​https://github.com/django/django/blob/master/docs/ref/models/querysets.txt#L1886

I think something along the lines of:

get_or_create() can be used with Q objects by chaining them together like so:

An example

When this is done, the logic performs as above, but matches are made according to the query in the Q object.

I imagine this also works for update_or_create, but I'm not sure how to document that too. Maybe just a quick mention:

update_or_create() can be used with Q objects using the same technique as documented above for get_or_create()