public void RemoveTournamentAdministrator(Tournament tournament, ApplicationUser user)
        {
            TournamentAdministrator tournamentAdmin = _context.TournamentAdministrators
                                                      .SingleOrDefault(ta => ta.ApplicationUserId == new Guid(user.Id) &&
                                                                       ta.TournamentId == tournament.TournamentId);

            _context.TournamentAdministrators.Remove(tournamentAdmin);
            _context.SaveChangesAsync();
        }
        public void AddTournamentAdministrator(Tournament tournament, ApplicationUser user)
        {
            TournamentAdministrator tournamentAdmin = new TournamentAdministrator()
            {
                User = user,
                ApplicationUserId = new Guid(user.Id),
                Tournament        = tournament
            };

            _context.Add(tournamentAdmin);
            _context.SaveChangesAsync();
        }