public async Task<IHttpActionResult> PutAchievement(int id, Achievement achievement)
        {
            if (!ModelState.IsValid)
            {
                return BadRequest(ModelState);
            }

            if (id != achievement.Id)
            {
                return BadRequest();
            }

            _db.Entry(achievement).State = EntityState.Modified;

            try
            {
                await _db.SaveChangesAsync();
            }
            catch (DbUpdateConcurrencyException)
            {
                if (!AchievementExists(id))
                {
                    return NotFound();
                }
                else
                {
                    throw;
                }
            }

            return StatusCode(HttpStatusCode.NoContent);
        }
        public async Task<IHttpActionResult> PostAchievement(Achievement achievement)
        {
            if (!ModelState.IsValid)
            {
                return BadRequest(ModelState);
            }

            _db.Achievements.Add(achievement);
            await _db.SaveChangesAsync();

            return CreatedAtRoute("DefaultApi", new { id = achievement.Id }, achievement);
        }