Fixed #20426 -- Added some extra info to the auth forms.

Thanks to Joel Hansson for the suggestion and Curtis Maloney for the initial
patch.
Added myself to committers.
Remove unnecessary and problematic parent class from SuccessMessageMixin

refs #16319, thanks to bmispelon for the catch
Replaced an antiquated pattern.

Thanks Lennart Regebro for pointing it out.
Modernize the CSRF migration helper.

Thanks Lennart Regebro for spotting that code.
Fix up company link.