Accessing Other Fields in Schema Transformations and Custom Errors

const schema = Schema.Struct({
  duration: Schema.DurationFromSelf,
  token: Schema.transformOrFail(
    Schema.Struct({..}),
    Schema.String,
    {
      strict: true,
      encode: (...) => { /* decrypt token and get the data or return error */ },
      decode: (...) => { /* encrypt token with 'duration' value and return the encrypted string or return error in case of any failure */ } 
  )
})