When Envoy terminates TLS, it sends along metadata about the client certificates
in an x-forwarded-client-cert
HTTP header. This library parses that header into
Go structs.
var req *http.Request
xfccHeader := req.Header.Get(xfccparser.ForwardedClientCertHeader)
clientCerts, err := xfccparser.ParseXFCCHeader(xfccHeader)
Thanks to Alec Thomas for help with the participle representation.