Okta Refresh Token Method

        [AllowAnonymous]
        [HttpPost("refresh")]
        public async Task<ActionResult<object>> HandleRefresh([FromBody] RefreshRequest req)
        {
            if (req.RefreshToken == "") {
                return BadRequest();
            }
            using (var client = new HttpClient())
            {
                var uri = new Uri($"https://{_oktaOptions.Value.OktaDomain}/oauth2/{_oktaOptions.Value.AuthorizationServerId}/v1/token");
                var content = new FormUrlEncodedContent(new[] {
                    new KeyValuePair<string, string>("grant_type",  "refresh_token"),
                    new KeyValuePair<string, string>("scope",  "offline_access openid"),
                    new KeyValuePair<string, string>("client_id",  _oktaOptions.Value.ClientId),
                    new KeyValuePair<string, string>("client_secret",  _oktaOptions.Value.ClientSecret),
                    new KeyValuePair<string, string>("refresh_token",  req.RefreshToken)
                });
                var request = new HttpRequestMessage
                {
                    Method = HttpMethod.Post,
                    RequestUri = uri,
                    Headers = {
                        { "Accept", "application/json" },
                    },
                    Content = content

                };
                var response = await client.SendAsync(request);
                if (response.IsSuccessStatusCode) {
                    return Ok(response.Content.ReadAsStringAsync().Result);
                }
                return BadRequest(response.Content.ReadAsStringAsync().Result);
            }
        }
    }