Add a template for rendering legacy and Django fieldsets.
Review Request #8376 — Created Sept. 1, 2016 and submitted
This is a combination of two backports, one for the new fieldsets
template, and one for adding support for Django fieldsets.
The new fieldsets template is available in
siteconfig/settings_fieldsets.html, unlike the new template which is in
forms/admin/form_fieldsets.html. The legacy location is used to
prevent breakages with users of Djblets, since it would require adding
The old template that this fieldset support came from only supported
our old custom version of fieldsets, rather than Django's version.
In Djblets 0.10, we added support for both. This change is backporting
that to the new fieldsets template.
Tested with old-style and new-style fieldsets.
Unit tests pass.