public Task <int> Add(ProposalModel model)
        {
            var entity = Proposal.FromModel(model);

            dbContext.Proposals.Add(entity);
            return(dbContext.SaveChangesAsync());
        }
        public Task <int> Add(ConferenceModel model)
        {
            var entity = Conference.FromModel(model);

            dbContext.Conferences.Add(entity);
            return(dbContext.SaveChangesAsync());
        }
        public Task <int> Add(AttendeeModel attendee)
        {
            var entity = Attendee.FromModel(attendee);

            dbContext.Attendees.Add(entity);
            return(dbContext.SaveChangesAsync());
        }