Add form class argument to comment_form()

[flixos90]

When using the comment_form() function, it is currently not possible to adjust the class of the form. ID can be adjusted, and for example the submit's ID and class can also be adjusted. So I thought it would be straightforward to add the same for the form tag itself.

Use-case: I'm using a theme based on Bootstrap, and I would like to have a horizontal comment form for which I need to apply a class 'form-horizontal' to the form tag. Right now I can only do that by outputting the whole form manually, including all the actions and filters which is a pain to manage when I would rather just create markup. I'd much rather use the built-in comment_form() function instead and only adjust the arguments there.

[flixos90]

Patch to address the issue (includes docs)

[DrewAPicture]

Hi @flixos90, thanks for the patch. Could you also add the new argument to the list in the 4.4.0 changelog entry in the DocBlock please?

[flixos90]

Added new argument to changelog

[flixos90]

@DrewAPicture Thanks for the quick response! The new argument is now in the DocBlock.

[DrewAPicture]

In 34871:

Template: Introduce a new class_form argument in comment_form(), allowing customization of the form class attribute.

The static 'comment-form' class was originally added to comment_form() in [24525]. This new argument should provide needed flexibility in styling the comment form further.

Props flixos90.
Fixes #34170. See #23851.