make configurable in which part of the OIDC exchange custom claims should be sent

In the authorization code flow, custom claims can be sent either in the "id_token" or by querying the "userinfo".

If the client made a preference as to where the claims should be by setting the "claims parameter", the module honours this and sends accordingly.

If no preference is indicated by the client, the module currently sends custom claims always via the userinfo endpoint. As per OIDC core spec, the claims /could/ alternatively be sent directly in the id_token.

The issue at hand suggests to make configurable where a specific custom claim should be sent. The suggested place is the OIDC-to-SAML attribute mapping table, as this lists every single claim

Example, for a hypothetical custom claim "foobar":

    // The default translate table from SAML attributes to OIDC claims.
    ModuleConfig::OPTION_AUTH_SAML_TO_OIDC_TRANSLATE_TABLE => [
...
          'foobar' => [
             'attribute' => 'urn:x-randomvendor:attibute-xyz',
             'dest' => 'userinfo' # or 'id_token'
          ],

There should be a backwards-compatible default (single-string array defaults to "userinfo", to keep the current behaviour).

An open question is how to prioritise if the client did send a claim parameter, but the configured destination differs from the configured destination - which one wins?

Commencez par la table de mappage des attributs OIDC-to-SAML et suivez le authorization code flow qui envoie les custom claims au userinfo endpoint ou dans le id_token. Définissez comment le mappage prend en charge une valeur par défaut rétrocompatible de userinfo, puis déterminez comment un paramètre de claims explicite du client doit interagir avec la destination configurée. Le travail est terminé lorsque chaque custom claim configuré est correctement acheminé sans modifier les valeurs par défaut existantes.