Corporate users behind TLS-inspecting proxies (Zscaler, Netskope,
Palo Alto, in-house mitmproxy fleets) need to add the proxy's
intermediate CA to the trusted-roots set so the deepseek client
doesn't fail with `unable to get local issuer certificate`.
The reqwest builder already trusts the platform's system store
via native-tls. This adds opt-in support for the conventional
`SSL_CERT_FILE` env var so users can point at their own bundle:
* New `add_extra_root_certs(builder, path)` helper reads the
file, tries `Certificate::from_pem_bundle` (covers single-cert
files too), falls back to `from_der` for binary cert files.
* Wired into `build_http_client` when `SSL_CERT_FILE` is set
and non-empty. Failures log a warning via the existing
`logging::warn` channel and return the builder unchanged —
the existing system trust still applies, so a malformed env
var degrades gracefully instead of bricking the launch.
* Each successful load logs `info` with the cert count so
operators can confirm their bundle was picked up.
Documented in `docs/CONFIGURATION.md`'s environment-variables
list alongside the existing TLS-related notes.
No new dependency — reqwest's `native-tls` feature already
exposes `Certificate::from_pem_bundle` / `from_der`.
Hunter Bown
604edc9f83