This adds a couple of key improvements to the Forward Auth SSO implementation. Primarily it adds an included cookies setting which allows filtering cookies to the authorization server. Secondly it fixes a bug where the headerCopyIncluded function was case-sensitive. Documentation in the code and on the web UI is clearer to resolve some common questions and issues. Lastly it moves a lot of funcs to the util.go file and adds fairly comprehensive tests.
This adds basic support for forwarded authentication similar to caddy and traefik. This replaces Authelia SSO as it effectively covers exactly the same use cases.
