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

OIDC-to-SAML 属性マッピングテーブルから始め、custom claims を userinfo endpoint または id_token に送信する authorization code flow を追跡します。マッピングが userinfo の後方互換なデフォルトをどのようにサポートするかを定義し、そのうえで、明示的なクライアントの claims パラメーターが設定された送信先とどのように相互作用すべきかを明らかにします。既存のデフォルトを変更せず、設定された各 custom claim が正しくルーティングされれば完了です。

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?