Allow definition of custom types

[lpil]

Hello! Thank you for Grape. :)

We would like to be able to do something like this:

params do
  requires :id, type: UUID, desc: 'Content id.'
end

Rather then set the type as String, and then validate the format of that string. We realise we can achieve the same result using validators, but we think this would be a more elegant, declarative syntax.

Is this possible?

Thanks,
Louis

[dblock]

It probably is with a bit of work - you need to dig through the implementation because type is something special. Grape's validation is based on Virtus (https://github.com/solnic/virtus), so I think defining a Virtus type for UUID would be sufficient. I don't know exactly how, will leave this open as a feature request.

[dblock]

Closed via #1039.