fix: use Debug format for S3/object store errors to include full error chain

The Display format of object_store and serde_json errors only shows the
top-level message (e.g. "Generic AWS error: an error occurred while loading
credentials") while the Debug format includes the full source chain with
actionable details about which credential provider failed and why.

Changed in:
- s3_helpers.rs: object store client build errors, resource parsing errors
- triggers/http/handler.rs: S3 file retrieval errors

Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com>

backend/windmill-api/src/triggers/http/handler.rs

@@ -963,7 +963,7 @@ async fn route_job(
 
             let s3_object = s3_object.map_err(|err| {
                 tracing::warn!("Error retrieving file from S3: {:?}", err);
-                Error::internal_err(format!("Error retrieving file: {}", err.to_string()))
+                Error::internal_err(format!("Error retrieving file: {:?}", err))
             })?;
 
             let mut response_headers = http::HeaderMap::new();

backend/windmill-common/src/s3_helpers.rs

@@ -793,8 +793,8 @@ pub async fn build_s3_client(s3_resource_ref: &S3Resource) -> error::Result<Arc<
     let store = store_builder.build().map_err(|err| {
         tracing::error!("Error building object store client: {:?}", err);
         error::Error::internal_err(format!(
-            "Error building object store client: {}",
-            err.to_string()
+            "Error building object store client: {:?}",
+            err
         ))
     })?;
 
@@ -860,8 +860,8 @@ fn build_azure_blob_client(
     let store = store_builder.build().map_err(|err| {
         tracing::error!("Error building object store client: {:?}", err);
         error::Error::internal_err(format!(
-            "Error building object store client: {}",
-            err.to_string()
+            "Error building object store client: {:?}",
+            err
         ))
     })?;
 
@@ -900,8 +900,8 @@ async fn build_gcs_client(gcs_resource_ref: &GcsResource) -> error::Result<Arc<d
         .map_err(|err| {
             tracing::error!("Error building GCS object store client: {:?}", err);
             error::Error::internal_err(format!(
-                "Error building GCS object store client: {}",
-                err.to_string()
+                "Error building GCS object store client: {:?}",
+                err
             ))
         })?;
 
@@ -1257,21 +1257,21 @@ pub fn lfs_to_object_store_resource(
     match lfs {
         LargeFileStorage::S3Storage(_) | LargeFileStorage::S3AwsOidc(_) => {
             let s3_resource: S3Resource = serde_json::from_value(resource_value).map_err(|e| {
-                error::Error::internal_err(format!("Error parsing S3 resource: {}", e))
+                error::Error::internal_err(format!("Error parsing S3 resource: {e:?}"))
             })?;
             Ok(ObjectStoreResource::S3(s3_resource))
         }
         LargeFileStorage::AzureBlobStorage(_) | LargeFileStorage::AzureWorkloadIdentity(_) => {
             let azure_blob_resource: AzureBlobResource = serde_json::from_value(resource_value)
                 .map_err(|e| {
-                    error::Error::internal_err(format!("Error parsing Azure Blob resource: {}", e))
+                    error::Error::internal_err(format!("Error parsing Azure Blob resource: {e:?}"))
                 })?;
             Ok(ObjectStoreResource::Azure(azure_blob_resource))
         }
         LargeFileStorage::GoogleCloudStorage(_) => {
             let gcs_resource: GcsResource =
                 serde_json::from_value(resource_value).map_err(|e| {
-                    error::Error::internal_err(format!("Error parsing GCS resource: {}", e))
+                    error::Error::internal_err(format!("Error parsing GCS resource: {e:?}"))
                 })?;
             Ok(ObjectStoreResource::Gcs(gcs_resource))
         }