events: Raise error when user is registering to the event multiple times
events: Raise error when user is registering to the event multiple times

matus-stehlik/roots,tbabej/roots,rtrembecky/roots,rtrembecky/roots,tbabej/roots,rtrembecky/roots,matus-stehlik/roots,matus-stehlik/roots,tbabej/roots