public IHttpActionResult Update(ArtistDataModel artist)
        {
            if (artist == null || artist.Id == null)
            {
                return this.BadRequest("You must provide artist ID.");
            }

            var existingArtist = this.db.Artists.Find(artist.Id);
            if (existingArtist == null)
            {
                return this.BadRequest("An artist with the provided ID do not exist.");
            }

            if (artist.Name != null)
            {
                existingArtist.Name = artist.Name;
            }

            if (artist.Country != null)
            {
                existingArtist.Country = artist.Country;
            }

            if (artist.Birthday != null)
            {
                existingArtist.Birthday = artist.Birthday;
            }
            
            this.db.SaveChanges();

            return this.Ok(existingArtist);
        }
        public IHttpActionResult Create(ArtistDataModel newArtist)
        {
            if (newArtist == null || newArtist.Name == null)
            {
                return this.BadRequest("You must provide artist name.");
            }

            var artist = new Artist
            {
                Name = newArtist.Name, 
                Country = newArtist.Country,
                Birthday = newArtist.Birthday
            };

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

            return this.Ok(artist);
        }