Fix support for multiple LDAP user formats (#11276)

Fixes support for using multiple base DNs for user search in the LDAP directory
allowing users from different subtrees in the LDAP hierarchy to request
credentials.

- The username in the produced credentials is now the full DN of the LDAP user
to disambiguate users in different base DNs.

cmd/config/identity/ldap/legacy.go

@@ -47,7 +47,7 @@ func SetIdentityLDAP(s config.Config, ldapArgs Config) {
 		},
 		config.KV{
 			Key:   GroupSearchBaseDN,
-			Value: ldapArgs.GroupSearchBaseDN,
+			Value: ldapArgs.GroupSearchBaseDistName,
 		},
 	}
 }