Exposed :key (in addition to :message)

I have a use case where I could do with :key exposed.

If I echo out my errors, on some occasions I output the errors in a single block then treat them using JS (usually moving them to an element on the page by the ID stored in a data attribute).

If I want to print <li data-key=":key">:message</li>, I cannot currently access the :key part (where :key is the ID of the associated field).

Being able to do this (as adjusted) allows a user to identify exactly what field an individual message was associated with e.g. when using ->all(), and is a simple exposure of data already held.