remote: T8829: fall back to GET when HEAD is not supported

HttpC.download() always probed remote URLs with HEAD before GET to
discover redirects and Content-Length. Some APIs (e.g. AbuseIPDB)
reject HEAD with 405 Method Not Allowed, causing firewall remote-group
downloads to fail and leave empty cached list files.

Treat HEAD 405/501 as unsupported and proceed with GET using the
original URL. When HEAD does not provide Content-Length, read it from
the GET response headers instead. Validate available storage after
determining file size and before opening the destination file.

Log sanitized download errors in vyos-domain-resolver when a remote-
group list-file fetch fails. Add unit tests with mock servers that
return 405 or 501 on HEAD and 200 on GET.

0 files changed, 0 insertions, 0 deletions