API: SS_TRUSTED_PROXY_HOST_HEADER replace with middleware config
API: SS_TRUSTED_PROXY_PROTOCOL_HEADER replace with middleware config
API: SS_TRUSTED_PROXY_IP_HEADER replace with middleware config
API: Front-End-Https = “on” header no longer supported
This middleware replaces the TRUSTED_PROXY setting and shifts its
configuration out of the env vars and bootstrap and into the Director
flow.
API Remove Director::$test_servers / $dev_servers
API Remove MODULES_PATH / MODULES_DIR constants
ENHANCEMENT Injector backtick syntax now supports environment variables as well as constants
Fixes#6588
