Delete a Booking

[xShirokuma]

Delete an existing booking.

• An authenticated user is required for a successful response
• Only the owner of the booking or the owner of the spot is authorized to
  delete the booking
• Booking record is removed from the database after request
• Success response includes a message indicating a successful deletion
• Error response with status 404 is given when a spot does not exist with
  the provided id
• Error response with status 400 is given when it is past the booking's
  startDate (no deleting of current or past bookings)