Generated model for id:Guid is incorrect

[avallee]

Ran dotnet saturn gen.json test test id:guid other:string and got this output which does not build (isNull u.id).

namespace test

[<CLIMutable>]
type test = {
  id: System.Guid
  other: string
}

module Validation =
  let validate v =
    let validators = [
      fun u -> if isNull u.id then Some ("id", "Id shouldn't be empty") else None
    ]

    validators
    |> List.fold (fun acc e ->
      match e v with
      | Some (k,v) -> Map.add k v acc
      | None -> acc
    ) Map.empty

I would think that for a Guid, it'd be something like a Guid.Empty = u.id.

[kierepka]

I made this same change:

let validators = [
      fun u -> if (u.id=System.Guid.Empty) then Some ("id", "Id shouldn't be empty") else None
    ]

But I got this error: ```

ERROR #500
Error parsing column 0 (id=6511E9C7-0046-4EBC-B94E-B87591BDB5DC - String)
BioMindsXR_SRV
at Users.Controller.indexAction@14-1.Invoke(FSharpResult`2 _arg1) in D:\GitHub\BioMinds_SRV\src\BioMindsXR_SRV\Users\UsersController.fs:line 18 at

Inner error:`
Invalid cast from 'System.String' to 'System.Guid'`