Network errors to the Hetzner API are logged without their cause #77

When robotlb can't reach the Hetzner API, the log says "error sending request for url (...)" and nothing about why. I saw this for about nine hours on a cluster running a build of the open PRs. Every reconcile of every Service failed with that line, then it recovered by itself without a restart. From the log I can't tell whether it was DNS, TLS, a refused connection on the way out of the cluster, or Hetzner.

The cause is lost in the error formatting. describe() from #37 returns error.to_string() for everything that is not a response error. The Display of reqwest::Error only prints the top level, and the actual reason sits in source().

I'd like describe() to append the source() chain, so the log and the warning event say what failed.