Custom serialization of failed tests' arguments

[ashnur]

Currently it's just a JSON.stringify from here:
https://github.com/robotlolita/claire/blob/df007a398a89100579d06be4246226c075126715/src/check.ls#L155

This could remain a good default, but certain scenarios would greatly benefit if the arguments could be resolved in the context generated for them.

Any kind of id arguments for example which would'be required from a database.