Add details to the i18n documentation for translation of model classes (relations and methods)

[maxime.petazzoni@…]

While working on the internationalization of a Django application recently, I had a hard time finding how to translate a few things used in model classes : relations and model methods, when used for columns or fields in the Django admin site.

I finally found the solutions from some random code snippet on the web, but I think this really belongs to Django's excellent documentation, so you'll find attached a patch to add a few details on how this is done.

I know there's an i18n documentation refactoring going on in #10260. If my patch needs to be reworked on top of that refactoring once it's checked in, please let me know.

[maxime.petazzoni@…]

Adding a section "Notes on model classes translation" to the i18n documentation

[maxime.petazzoni@…]

Fixing typo in bug summary.

[Russell Keith-Magee]

Will need to be updated to be integrated into the changes for #10260, but otherwise seems reasonable.

[Ramiro Morales]

Patch updated to post i18n docs refactor.

[James Bennett]

This isn't critical to 1.2; we can always go back and improve documentation as needed, but attention right now should focus on actual bugs.

[Tim Graham]

(In [15103]) [1.2.X] Fixed #12193 - Add details to the i18n documentation for translation of model classes (relations and methods). Thanks Maxime Petazzoni and Ramiro for work on the patch.

Backport of r15102 from trunk.