Align default login attribute across services

Up to now the builtin lico was using the "username" as the login
attribute, while the proxy (and to some extend the auth-basic) service
tried to uniquely identify users by mail address. This aligns the
default configuration of the services to use the username everywhere.

Fixes: #4039

services/auth-basic/pkg/config/defaults/defaultconfig.go

@@ -43,7 +43,7 @@ func DefaultConfig() *config.Config {
 				GroupBaseDN:      "ou=groups,o=libregraph-idm",
 				UserScope:        "sub",
 				GroupScope:       "sub",
-				LoginAttributes:  []string{"uid", "mail"},
+				LoginAttributes:  []string{"uid"},
 				UserFilter:       "",
 				GroupFilter:      "",
 				UserObjectClass:  "inetOrgPerson",