Merge branch 'dev' into 'destination-tests'

# Conflicts:
#   modules/flight/src/main/java/cz/muni/fi/pa165/flight/data/Flight.java
#   modules/flight/src/main/java/cz/muni/fi/pa165/flight/service/FlightController.java
#   modules/flight/src/main/java/cz/muni/fi/pa165/flight/service/FlightService.java