Currently, user's identity headers are always inserted to downstream
request. For privacy reason, it would be better to not insert these
headers by default, and let user chose whether to include these headers
per=policy basis.
Fixes#702
* config: add RemoveRequestHeaders
Currently, we have "set_request_headers" config, which reflects envoy
route.Route.RequestHeadersToAdd. This commit add new config
"remove_request_headers", which reflects envoy RequestHeadersToRemove.
This is also a preparation for future PRs to implement disable user
identity in request headers feature.
* integration: add test for remove_request_headers
* docs: add documentation/changelog for remove_request_headers
* envoy: support autocert
* envoy: fallback to http host routing if sni fails to match
* update comment
* envoy: renew certs when necessary
* fix tests