chore: Add more debug log for gcs to help us diagnose

Signed-off-by: Xuanwo <github@xuanwo.io>

src/cache/cache.rs

@@ -425,11 +425,15 @@ impl Storage for opendal::Operator {
             }
         };
 
-        if can_write {
-            Ok(CacheMode::ReadWrite)
+        let mode = if can_write {
+            CacheMode::ReadWrite
         } else {
-            Ok(CacheMode::ReadOnly)
-        }
+            CacheMode::ReadOnly
+        };
+
+        debug!("storage check result: {mode:?}");
+
+        Ok(mode)
     }
 
     fn location(&self) -> String {

src/cache/gcs.rs

@@ -95,11 +95,15 @@ struct TaskClusterTokenLoader {
 
 impl GoogleTokenLoad for TaskClusterTokenLoader {
     fn load_token(&self) -> Result<Option<GoogleToken>> {
+        debug!("gcs: start to load token from: {}", &self.url);
+
         let res = self.client.get(&self.url).send()?;
 
         if res.status().is_success() {
             let resp = res.json::<TaskClusterToken>()?;
 
+            debug!("gcs: token load succeeded for scope: {}", &self.scope);
+
             // TODO: we can parse expire time instead using hardcode 1 hour.
             Ok(Some(GoogleToken::new(
                 &resp.access_token,