## What changed
- Add optional `network.mitm_ca` configuration with `certificate_file` and
`private_key_file` for trusted proxy configuration. Require MITM to be enabled
and retain the generated CA when no external CA is configured.
- Validate absolute paths, regular files, file sizes, certificate/key matching,
and Unix private-key permissions. Reject symlinks on Unix, private keys embedded
in certificate files, and external private keys on non-Unix platforms.
- Store derived external-CA trust bundles in the proxy artifact directory,
include only certificates, and skip inherited generated bundles to avoid
retaining stale roots.
- Preserve MITM for external CAs when disabling credential brokerage. Reject
external CA configuration for remote execution, even when the proxy is disabled,
and reject unknown fields in `NetworkProxyConfig`.
- Default the upstream request version adapter to HTTP/1.1 and remove the request
URI from upstream request failure context.
## Testing
Add regression coverage for external CA configuration, mismatched keys, embedded
private keys, non-Unix rejection, trust-bundle placement and contents, stale-root
exclusion, credential-broker toggling, and remote configuration rejection.
GitOrigin-RevId: cb209295c19fbe53a9fa0194f11ff06acccabef6
viyatb-oai
e4dba902ab