Field iteration support types

pub enum FieldValue {
  FvBool   { v: boolean },
  FvInt    { v: integer },
  FvLong   { v: long },
  FvFloat  { v: float },
  FvSingle { v: single },
  FvChar   { v: character },
  FvText   { v: text }
}

Wraps a field value in a type-discriminated enum for compile-time field iteration.

pub struct StructField {
  name:  text not null,
  value: FieldValue,
}

Represents a single struct field during compile-time iteration.