public String getIssuer() throws GuacamoleException {
        return environment.getRequiredProperty(OPENID_ISSUER);
    }
Returns the issuer to expect for all received ID tokens, as configured
with guacamole.properties.

@return
    The issuer to expect for all received ID tokens, as configured with
    guacamole.properties.

@throws GuacamoleException
    If guacamole.properties cannot be parsed, or if the issuer property
    is missing.
extensions/guacamole-auth-sso/modules/guacamole-auth-sso-openid/src/main/java/org/apache/guacamole/auth/openid/conf/ConfigurationService.java