Config languages (and Dhall)

I guess the idea was mainly for upstream projects (like GHC) to more conveniently maintain their own metadata, such as GHC nightlies. Their yaml is currently generated with some sad python script and there isn’t much I can do to communicate to projects “hey, the metadata format changed, here’s how you update your scripts”. Also, yaml is super loose and the yaml/aeson parsers accept unknown keys. So your metadata might be slightly wrong (mistyped an optional field), but still parse. Yes, they could simply use GHCup as a library, which I also do here, but my hunch is that is not very appealing, since they didn’t do that. So the criteria is: * validation * assisting with generation of the metadata from some input * ergonomics (no one wants to learn a new complicated language to do this boring work)