Replace model icon choices with new icon set

In the core/utils/model_helpers.py is a list of all icons, to use as CHOICES for model fields. These need to be replaced with the icon names from the new icon set.

Ideally, this should be removed, and django-iconify should get a mechanism to return icon choices from its data set.

AlekSIS/libs/django-iconify#8 (closed)

@ZugBahnHof Please check whether AlekSIS/libs/django-iconify!6 (merged) works and is enough.

Please note that you can now use ICONIFY_COLLECTIONS_ALLOWED in settings to limit icons available to a set of collections.

Should work now (pipeline won't however, until a new version of django-iconify is released). Also made changes there in django-iconify. I thought about maybe logging a warning, if an illegal icon set is requested, what do you think?

What's also pretty important: every app that uses these choices now needs to change the respective templates. I know from my head, Hjelp and Alsijil need changes, but every official app needs to be checked (maybe together with the new icon set migration issues)

assigned to @nik

assigned to @ZugBahnHof and unassigned @nik

created branch 674-replace-model-icon-choices-with-new-icon-set to address this issue

mentioned in merge request !1048 (merged)

Before:

After:

closed with merge request !1048 (merged)

mentioned in commit 2abc196e