public String getGroupAttribute() throws GuacamoleException {
        return environment.getProperty(SAML_GROUP_ATTRIBUTE, "groups");
    }
Return the name of the attribute that will be supplied by the identity
provider that contains the groups of which this user is a member.

@return
    The name of the attribute that contains the user groups.

@throws GuacamoleException 
    If guacamole.properties cannot be parsed.
extensions/guacamole-auth-sso/modules/guacamole-auth-sso-saml/src/main/java/org/apache/guacamole/auth/saml/conf/ConfigurationService.java