/**
 * Converts a locale string from hyphen format (e.g., "en-US")
 * to underscore format (e.g., "en_US").
 *
 * Useful for APIs or systems that expect locales with underscores.
 *
 * @param {string} locale - The locale string in BCP 47 format (e.g., "en-US").
 * @returns {string} The normalized locale string using underscores (e.g., "en_US").
 *
 * @example
 * normalizeLocaleUnderscore("en-US"); // "en_US"
 */
export const normalizeLocaleUnderscore = (locale) => {
  return locale.split('-').join('_');
};