a DAV client tells you almost nothing when it fails — iOS reports every setup
failure as "Cannot connect using SSL" regardless of cause — so the only way to
know whether a phone ever asked for an address book is to record that it did.
one line per proxied request with the client's own user-agent, and a warning
when a credential is present but wrong. a missing credential is the normal
opening move and stays unlogged; a wrong one is indistinguishable from it at
the client end, where both just say "password incorrect".
no body is ever logged.
Co-Authored-By: Claude Opus 5 <noreply@anthropic.com>