[Feature Request] Use Enum field type in JSON type

**Is your feature request related to a problem? Please describe.**
I'd like to be able to do this (or a similar alternative solution):

```
enum TagType {
    One
    Two
    Three
}

type TestData {
    tag     TagType?
    eventId String?
}

model Test {
    id   String   @id @default(cuid())
    data TestData @json
}
```