/**
 * Serializes a query tags dictionary into a string for use in confOverlay.
 *
 * Format: comma-separated key:value pairs, e.g. "key1:value1,key2:value2"
 * - If a value is null or undefined, the key is included without a colon or value
 * - Backslashes in keys are escaped; other special characters in keys are not escaped
 * - Special characters (backslash, colon, comma) in values are backslash-escaped
 *
 * @param queryTags - dictionary of query tag key-value pairs
 * @returns serialized string, or undefined if input is empty/null/undefined
 */
export default function serializeQueryTags(queryTags: Record<string, string | null | undefined> | null | undefined): string | undefined;