export function sanitize(data: FormData, key: string): string;
export function sanitize<Fallback>(
	data: FormData,
	key: string,
	fallback: Fallback
): string | Fallback;
export function sanitize<Fallback>(
	data: FormData,
	key: string,
	fallback?: Fallback
): string | Fallback {
	const val = data.get(key);
	if (val !== null) return val.toString().trim();

	if (fallback !== undefined) return fallback;
	throw new Error(`Missing required field: ${key}`);
}