SECURITY UPDATE: buffer overflow in the gRPC upstream request builder via
overlong HTTP/2 header fields
debian/patches/CVE-2026-42055.patch: reject a method name, URI, host,
configured header name or value, or forwarded client header name or
value longer than NGX_HTTP_V2_MAX_FIELD in
ngx_http_grpc_create_request(), so an oversized field can no longer
overflow the HPACK integer encoding the request buffer was sized for