public async Task <ActionResult <UserCredential> > PostUserCredential(UserCredential userCredential)
        {
            // Set Token
            userCredential = await ExchangeAuthCode(userCredential);

            //if (_context.UserCredential.Find(userCredential.ClientCredentials.ClientId) == null)
            //{
            //    _context.UserCredential.Add(userCredential);
            //    await _context.SaveChangesAsync();
            //    return CreatedAtAction("GetUserCredential", new { id = userCredential.Id }, userCredential);
            //}
            //else
            //{
            //    throw new
            //}
            _context.UserCredential.Add(userCredential);
            await _context.SaveChangesAsync();

            return(CreatedAtAction("GetUserCredential", new { id = userCredential.Id }, userCredential));
        }