add explaining comment about AWS S3 bug

Co-authored-by: Joshua Nelson <[email protected]>

Author: syphar

src/storage/s3.rs

@@ -121,6 +121,8 @@ impl S3Backend {
 
             let date_updated = res
                 .last_modified
+                // This is a bug from AWS, it should always have a modified date of when it was created if nothing else.
+                // Workaround it by passing now as the modification time, since the exact time doesn't really matter.
                 .map_or(Ok(Utc::now()), |lm| parse_timespec(&lm))?;
 
             let compression = res.content_encoding.and_then(|s| s.parse().ok());