Address review feedback on PR #2044.
safehttp.Transport():
* Clone http.DefaultTransport instead of building a bare &http.Transport{} so
Proxy, ForceAttemptHTTP2, MaxIdleConns, IdleConnTimeout, TLSHandshakeTimeout
and ExpectContinueTimeout are inherited (the bare struct loses them all).
Verified by new TestTransport_PreservesDefaultTransportSettings.
* TestTransport_AllowsPublic: bound the dial of TEST-NET-3 with a 100ms
context so the test does not depend on real-world routing of 203.0.113.0/24,
and drop the dead dialer var.
proxy/image.go:
* Document Image.Transport contract: nil installs safehttp.Transport (SSRF-safe);
caller-supplied transport is the caller's responsibility.
* Replace the misleading "SSRF mitigated by safehttp.Transport" nolint comments
with one that points at the documented contract above.
Dmitry VerkhoturovandUmputun
3b1d7be6fc