List the tour's stops that can accept carried-back cargo, with the key each one needs. Cargo a receiver refused stays on the vehicle and is unloaded at one of your cross-docking locations later in the tour; the advance that records it (POST /tours/{tourId}/actions with carryBackUnloads) also requires the carryBackStopKey of the stop it happened at, and this is where that key comes from. Only stops with a location on file appear; of those, act only on the ones answering hasCrossdock: true. The keys are computed against the tour as the server holds it, so re-read this after a stop reorder.