public String getHttpAuthHeader() throws GuacamoleException {
        return environment.getProperty(
            HTTPHeaderGuacamoleProperties.HTTP_AUTH_HEADER,
            "REMOTE_USER"
        );
    }
Returns the header of the HTTP server as configured with
guacamole.properties used for HTTP authentication.
By default, this will be "REMOTE_USER".

@return
    The header used for HTTP authentication, as configured with
    guacamole.properties.

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