public async Task<IHttpActionResult> PostUpdatePassword(AuthRepository.PostModel userModel)
        {
            if (!ModelState.IsValid) return BadRequest(ModelState);

            IdentityResult result = await _repo.ChangePassword(userModel);
            IHttpActionResult errorResult = GetErrorResult(result);

            if (errorResult != null) return errorResult;
            return Ok();
        }
        public override async Task GrantResourceOwnerCredentials(OAuthGrantResourceOwnerCredentialsContext context)
        {
 
            context.OwinContext.Response.Headers.Add("Access-Control-Allow-Origin", new[] { "*" });
 
            using (AuthRepository _repo = new AuthRepository())
            {
                IdentityUser user = await _repo.FindUser(context.UserName, context.Password);
 
                if (user == null)
                {
                    context.SetError("invalid_grant", "The user name or password is incorrect.");
                    return;
                }
            }
 
            var identity = new ClaimsIdentity(context.Options.AuthenticationType);
            identity.AddClaim(new Claim("sub", context.UserName));
            identity.AddClaim(new Claim("role", "user"));
 
            context.Validated(identity);
        }