cubicweb-jsonschema #17073910 Format error responses following RFC7807 [validation pending]

RFC7807 - Problem Details for HTTP APIs provides a specification to format errors in HTTP response. We should use it.

prioritynormal
typeenhancement
done in0.2.0
load1.000
load left0.000
closed by#3c9a200e959b Implement RFC 7807 "Problem Details for HTTP APIs"