public IHttpActionResult Post(ArtistRequestModel model)
        {
            if (!this.ModelState.IsValid)
            {
                return this.BadRequest(this.ModelState);
            }

            var artist = new Artist
            {
                Name = model.Name,
                DateOfBirth = model.DateOfBirth
            };

            this.data.Artists.Add(artist);
            this.data.Artists.SaveChanges();

            return this.Ok(artist);
        }
        public IHttpActionResult Put(int id, ArtistRequestModel model)
        {
            if (!this.ModelState.IsValid)
            {
                return this.BadRequest(this.ModelState);
            }

            var artist = this.data.Artists
                .All()
                .FirstOrDefault(a => a.Id == id);

            if (artist == null)
            {
                return this.BadRequest("Artist with id " + id + " does not exist!");
            }

            artist.Name = model.Name;
            artist.DateOfBirth = model.DateOfBirth;

            this.data.Artists.Update(artist);
            this.data.Artists.SaveChanges();

            return this.Ok(model);
        }