add section about path based and domain based routing

[nabuskey]

No description provided.

[cmoulliard]

Many thanks as this section helps a lot to understand what idpbuilder do under the hood :-)

Some clarifications are still needed nevertheless and maybe they should be done using a separate PR.

To use a proper wording, here is what I propose to do:

Rename the arg/parameter --host to --domain-name to avoid to confuse the users as this argument is mainly used to route the requests to the host machine running the idpbuilder services (e.g argocd.cnoe.localtest.me, argocd.127.0.0.1.nip.io, argocd.example.com, etc) and is inline with the domain name (or subdomain like cnoe.localtest.me) as documented here: https://en.wikipedia.org/wiki/Domain_name

If we do what I suggest, then we can still propose the arg/parameter --user-path-routing as it exists as it allows the users to define the service to be accessed using the /path like cnoe.localtest.me/argocd, my.example.com/argocd, etc

[nabuskey]

We should do those in another PR. We need to document what we have now for user usability