AuthenticationController.cs

[HttpPost("register")]
        public async Task<IActionResult> Register([FromBody]UserCredentials credentials)
        {
            var alreadyExists = _context.Users.Any(u => u.Email == credentials.Email);

            if (alreadyExists)
            {
                return BadRequest("User already exists.");
            }

            (string hashedPass, string salt) = _hashingService.Hash(credentials.Password);

            var user = new User() { Email = credentials.Email, HashedPassword = hashedPass, Salt = salt };

            _context.Users.Add(user);
            await _context.SaveChangesAsync();

            return Ok(BuildToken(user.Email));
        }