Validation: default values on enum fields should be valid for the enum

[tomhoule]

The following schema currently (2.3.0) passes validation:

// This is your Prisma schema file,
// learn more about it in the docs: https://pris.ly/d/prisma-schema

datasource db {
  provider = "postgresql"
  url      = "postgresql://postgres:prisma@localhost:5432/testdb"
}

generator client {
  provider = "prisma-client-js"
}

model Cat {
  id    Int     @id
  meows Boolean @default(true)
  mood  CatMood @default(HANGRY)
}

enum CatMood {
  ANGRY
  HUNGRY
}

We do not validate that the @default() expression on the Cat.mood field is a variant of the CatMood enum. I think we could and should validate this.