Cleanup hooks

Hook 'metadata_hosted' and 'frontpage' are no longer called so do
not register hooks for them. Update the docs. Remove useless call
to configpage hook on admin module Test page (likely a copy-paste
error).

This was already the result after processing previously.

They were broken in master. The admin module now performs this
function. So to reduce duplication and to keep the metadata endpoints
simple, we remove the broken code here instead of fixing it.

The metadata endpoint requires an entityID, not authsource to find
the corresponding IdP. Which makes sense because that is the unique
identifier - different IdPs can make use of the same backend auth
source.

Fix broken translator in PHP 8.0;  for some reason it's pulling in v3 of the translation-contracts instead of v2.x

updated twig to version 3 and added wrapper for translation via symfony/twig-bridge

Co-authored-by: Ulrik nielsen <un@ipwsystems.dk>