Spike: allow extensions to contribute custom validators and serializers/deserializers for REST layer #1463
Description
Timeboxed to 1.5 weeks
Verify whether the current LB4 design allows extensions to contribute custom validators and serializers/deserializers for REST layer (see #750 and #118). If it does, then document how to write such extensions and identify any pain points to fix. If it does not, then propose a solution including a list of follow-up stories to make it happen.
Update
Also see what can be overridden vs. extended by adding more (ex: overriding date validator vs. adding a validator for a new type (while keeping support for the existing validators)).