MM-16861: Support Guest Authentication via AD/LDAP (#12690)

* Add config settings for LDAPSettings GuestFilter

* make error unique

* Update model/config.go

Co-Authored-By: Martin Kraft <martin@upspin.org>

* add LdapSetting isempty_guest_attribute to diagnostics.go

app/diagnostics.go

@@ -487,6 +487,7 @@ func (a *App) trackConfig() {
 		"isempty_group_filter":                   isDefault(*cfg.LdapSettings.GroupFilter, ""),
 		"isdefault_group_display_name_attribute": isDefault(*cfg.LdapSettings.GroupDisplayNameAttribute, model.LDAP_SETTINGS_DEFAULT_GROUP_DISPLAY_NAME_ATTRIBUTE),
 		"isdefault_group_id_attribute":           isDefault(*cfg.LdapSettings.GroupIdAttribute, model.LDAP_SETTINGS_DEFAULT_GROUP_ID_ATTRIBUTE),
+		"isempty_guest_filter":                   isDefault(*cfg.LdapSettings.GuestFilter, ""),
 	})
 
 	a.SendDiagnostic(TRACK_CONFIG_COMPLIANCE, map[string]interface{}{