The base structure is there but it's not used in a consistent manner in sources.
With this patch, you should be able to run a Tuleap ran on apache in HTTP and reverse proxified by nginx without having to tweak the local.inc (except trusted_proxies of course):
- force_ssl can be set to 1
- https_host can have a value
- no need to allow rest call in http
Remember: how to setup reverse proxy: https://tuleap-documentation.readthedocs.io/en/latest/administration-guide/howto.html#deploy-tuleap-behind-a-reverse-proxy