Retrieve list of existing build cache keys
With caches being immutable in 2.0, it would be very handy to be able to retrieve a list of the build cache keys. Ideally with some filtering options by repo or project, and also returning some useful metadata such as size, created_by_build_num, date_created and build_num_last_retrieved, date_last_retrieved, etc. Bonus points for the ability to retrieve cache contents, as inspecting the contents of these things can be very enlightening, as sometimes they don't contain what you think they do.
This would assist in "fault finding" of caches in the build process and greatly assist in effective cache utilisation.