Use DeviceCodeErrorResponseType::ExpiredToken for expired Device (#195)

It is good to use RequestTokenError::ServerResponse for expired
Device token instead of having a "Device code expired" string
is set to Other(). We see to it that they are have the same Error
with the error came from the endpoint. There was a timing
issue found that expired_token is returned from the endpoint
and sometimes the RequestTokenError::Other() was returned
after the expiration time given by the endpoint.

We make it uniform for easy error handling upon use.

src/lib.rs

@@ -2333,7 +2333,13 @@ where
         loop {
             let now = (*self.time_fn)();
             if now > timeout_dt {
-                break Err(RequestTokenError::Other("Device code expired".to_string()));
+                break Err(RequestTokenError::ServerResponse(
+                    DeviceCodeErrorResponse::new(
+                        DeviceCodeErrorResponseType::ExpiredToken,
+                        Some(String::from("This device code has expired.")),
+                        None,
+                    ),
+                ));
             }
 
             match self.process_response(http_client(self.prepare_request()?), interval) {
@@ -2372,7 +2378,13 @@ where
         loop {
             let now = (*self.time_fn)();
             if now > timeout_dt {
-                break Err(RequestTokenError::Other("Device code expired".to_string()));
+                break Err(RequestTokenError::ServerResponse(
+                    DeviceCodeErrorResponse::new(
+                        DeviceCodeErrorResponseType::ExpiredToken,
+                        Some(String::from("This device code has expired.")),
+                        None,
+                    ),
+                ));
             }
 
             match self.process_response(http_client(self.prepare_request()?).await, interval) {

src/tests.rs

@@ -2203,7 +2203,14 @@ fn test_device_token_authorization_timeout() {
         .err()
         .unwrap();
     match token {
-        RequestTokenError::Other(msg) => assert_eq!(msg, "Device code expired"),
+        RequestTokenError::ServerResponse(msg) => assert_eq!(
+            msg,
+            DeviceCodeErrorResponse::new(
+                DeviceCodeErrorResponseType::ExpiredToken,
+                Some(String::from("This device code has expired.")),
+                None,
+            )
+        ),
         _ => unreachable!("Error should be an expiry"),
     }
 }