public async Task <IActionResult> Login([FromBody] AuthenticationModel model)
        {
            if (!this.ModelState.IsValid)
            {
                return(Unauthorized());
            }

            var faceStream = new MemoryStream(Convert.FromBase64String(model.Face));

            if (await _identityService.Authenticate(model.Email, faceStream))
            {
                var userIdentity    = new System.Security.Principal.GenericIdentity(model.Email, "Biometric");
                var claimsPrincipal = new ClaimsPrincipal(userIdentity);
                await this.HttpContext.SignInAsync(AUTHENTICATION_SCHEME,
                                                   claimsPrincipal,
                                                   new AuthenticationProperties
                {
                    IsPersistent = true
                });

                return(Ok());
            }
            else
            {
                return(Unauthorized());
            }
        }