Callable setHtmlAttributes

[KDederichs]

Short description of what this feature will allow to do:
A new setHtmlAttributesCallable or something like that that'll do the same as the normal setHtmlAttributes but has access to the object.

Example of how to use this feature

After seeing in #2978 (comment) that you can build confirm modals with onClick attributes I was wondering if it would be possible to access the object in those so you can write more descriptive messages.

If you think that's something you'd be OK with let me know and I'll see if I can make a PR for this.