public async Task<IHttpActionResult> PutExercise(long id, Exercise exercise)
        {
            if (!ModelState.IsValid)
            {
                return BadRequest(ModelState);
            }

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

            if (db.Entry(exercise).Entity.Set.AspNetUser.Id.ToLower().CompareTo(user.Id.ToLower()) != 0)
                return NotFound();

            db.Entry(exercise).State = EntityState.Modified;

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

            return StatusCode(HttpStatusCode.NoContent);
        }
        public async Task<IHttpActionResult> PostExercise(Exercise exercise)
        {
            if (!ModelState.IsValid)
            {
                return BadRequest(ModelState);
            }

            db.Exercises.Add(exercise);
            await db.SaveChangesAsync();

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