Add tabbed translation admin

[julianwachholz]

This change adds simple tabbed UI for translated fields.

Update

This has been released as an independent package django-modeltrans-tabs

Important: The included JavaScript only supports Django 4.2 and up. I think it's a reasonable change as 3.2 is EOL soon (30 April 2024)

See also: #16 (comment)

[julianwachholz]

Hi @jieter I added a small test and added the mixin to the example app as well as fixed all pending linter errors.
Do you think this is ready to merge? This Admin integration would be the killer feature for this library I'm certain! :)

[jieter]

I really like the way this works, but I'm a little hesitant because of the amount of code we need to maintain to support it.

I added some superficial comments, I did not attempt to simplify the implementation yet, do you think there is potential to simplify it?

[julianwachholz]

Hey @jieter thanks for taking the time to have a look.

I agree with your sentiment that it's some completely new code that will have to be maintained in the future. I tried to keep it minimal using modern JS and no build step. The bulk of the code is required to synchronize the selected languages across all fields and supporting dynamically adding/removing inlines (i.e. fieldsets) in the Django Admin. I feel this sync feature allows for a much better editing experience for content moderators. Removing this feature would indeed get rid of a lot of code, but at the cost of UX.

One thing I thought about it that the Django Admin is by design a very slow moving thing, it has barely changed in the last decade. So keeping up to date with upstream is doable with relatively low effort (and I will gladly step up!).

PS: One thing I haven't mentioned is that the CSS variables referenced also support django-admin-interface

[julianwachholz]

@jieter do you have any thoughts?

[julianwachholz]

Hey @jieter it's been a while, do you not want to see this in django-modeltrans?