Clarify that add_fieldsets is not a standard ModelAdmin attribute

[vim@…]

The ModelAdmin.add_fieldsets attribute is not documented in the reference section for ModelAdmin options (ref/contrib/admin/#modeladmin-options), although it does appear in the example code for using a custom user model (topics/auth/customizing/#a-full-example), at the very end.

This is really useful. I think it should be documented more clearly, where people are likely to look for it.

[loic84]

UserAdmin.add_fieldsets is neither a public API nor a generic mechanism, it's an implementation detail of the UserAdmin class.

It wouldn't work on any other ModelAdmin unless you implement a custom ModelAdmin.get_fieldsets() that takes advantage of it.

[Tim Graham]

I was going to suggest we add a comment to that effect in topics/auth/customizing/#a-full-example

[loic84]

@timo: it's actually easier to document since we've fixed #18681 because the get_form() override is no longer necessary.

Unless of course you really need a different form, but in that case you can still leave out the flatten_fieldsets() bit.

[Tim Graham <timograham@…>]

In dce8945ea63c636a71f3bc5d610dccebc08c52eb:

Fixed #20762 -- Clarified that add_fieldsets is not a standard ModelAdmin attribute.

[Tim Graham <timograham@…>]

In cbfe56c856f9bb79fdd36d7e573c6156bb88720a:

[1.5.x] Fixed #20762 -- Clarified that add_fieldsets is not a standard ModelAdmin attribute.

Backport of dce8945ea6 from master

[Tim Graham <timograham@…>]

In 579ca9ee8d3c47ba46385db6beb2318cea97b123:

[1.6.x] Fixed #20762 -- Clarified that add_fieldsets is not a standard ModelAdmin attribute.

Backport of dce8945ea6 from master