5.颁发访问令牌

如果访问令牌请求是有效的且被授权，授权服务器如5.1节所述颁发访问令牌以及可选的刷新令牌。如果请求因客户端身份验证失败或无效，授权服务器如5.2节所述的返回错误响应。

5. Issuing an Access Token

   If the access token request is valid and authorized, the
   authorization server issues an access token and optional refresh
   token as described in Section 5.1.  If the request failed client
   authentication or is invalid, the authorization server returns an
   error response as described in Section 5.2.