async function saveConfiguration(configuration) {
  logger.debug('Saving MELCloud configuration...');
  const { username, password } = configuration;
  await this.gladys.variable.setValue(GLADYS_VARIABLES.USERNAME, username, this.serviceId);
  await this.gladys.variable.setValue(GLADYS_VARIABLES.PASSWORD, password, this.serviceId);

  return configuration;
}
@description Save MELCloud configuration.
@param {object} configuration - Configuration to save.
@returns {Promise} MELCloud configuration.
@example
await saveConfiguration({ username: '...', password: '...'});