HTTP header sanitizing

Envoy will potentially sanitize the following headers:

• x-envoy-decorator-operation

• x-envoy-downstream-service-node

• x-envoy-external-address

• x-envoy-ip-tags

• x-envoy-retry-grpc-on

• x-envoy-upstream-rq-timeout-alt-response

• x-forwarded-client-cert

• x-request-id