[SAML Groups] Allow linking accounts/domains to SAML groups

Most SAML IdPs are able to provide group information for the authenticated user in the form of a SAML attribute (with many values for each group the user is in). It would be useful to be able to use the groups in the same way that LDAP groups can, such as to give a user access to certain accounts.

Here is an example SAML response from AWS Identity Center showing how groups are formatted.

```xml


ourdomainhere.internal//S-1-5-21-3122984950-2570546592-4150994639-1732
ourdomainhere.internal//S-1-5-21-3122984950-2570546592-4150994639-2026
ourdomainhere.internal//S-1-5-21-3122984950-2570546592-4150994639-1814
ourdomainhere.internal//S-1-5-21-3122984950-2570546592-4150994639-1722
ourdomainhere.internal//S-1-5-21-3122984950-2570546592-4150994639-1748
ourdomainhere.internal//S-1-5-21-3122984950-2570546592-4150994639-1730
ourdomainhere.internal//S-1-5-21-3122984950-2570546592-4150994639-1953
ourdomainhere.internal//S-1-5-21-3122984950-2570546592-4150994639-1836


rhys@ourdomainhere.internal


```

This would be a useful feature to have as with more companies moving to a more "serverless" / "cloud-native" (insert your favourite buzzword here) it is becoming less common to an easy way to connect to the user directory with LDAP.

Inizia individuando la gestione esistente dei gruppi LDAP e i punti di ingresso per il parsing degli attributi SAML o per l'autenticazione. Definisci come l'attributo dei gruppi SAML multivalore debba essere associato all'accesso agli account o ai domini, quindi verifica che tali collegamenti forniscano lo stesso comportamento di accesso dei gruppi LDAP.

Scritto dal modello di indicizzazione a partire dal testo della issue.