Merge branch 'flight-error-text-fix' into 'develop'

[Enh] makes the flight-stewards error message better

See merge request !94

flight-module/src/main/java/cz/muni/fi/pa165/airportmanager/flightmodule/facade/FlightFacadeImpl.java

@@ -148,7 +148,7 @@ public class FlightFacadeImpl extends DomainFacadeImpl<Flight, FlightInsertDto,
     private void checkCorrectArguments(String token, List<StewardFindDto> stewards, List<UUID> stewards2,
                                        UUID airlineId, UUID planeId) {
         if (stewards2.size() != (stewards.size())) {
-            throw new ObjectNotFoundException("Unknown steward was provided");
+            throw new ObjectNotFoundException("Unknown or duplicate steward was provided");
         }
 
         if  (airlineService.retrieve(airlineId, token) == null) {