We can, for example, see a crate and see what edition it is, or see what authors it has.

Something we want is a general purpose reverse list of this stuff, and so we can go to a page and see all crates using the 2015 edition (in principle), or go to an author and see all the crates they've made. We may well want this for ALL metadata; license, publication dates, etc, and so want a general-purpose framework for producing it.