val bookings: F[BookingKey => EitherK[Booking, BookingCommandRejection, F]] =
  genericAkkaRuntime.runBehavior(/*...*/)

// Type alias for simplicity.
// Equivalent to:
// BookingKey => F[Booking[λ[α => F[Either[BookingCommandRejection, α]]]]]
type Bookings[F[_]] = Entities.Rejectable[BookingKey, Booking, F, BookingCommandRejection]

val adaptedBookings: F[Bookings[F]] =
  bookings.map(Eventsourced.Entities.fromEitherK(_))