/**
 * Canonicalizes an OIDC issuer URL for equivalence comparison. Two URLs
 * that normalize to the same string refer to the same issuer, which is
 * what `discoverOIDC` uses to build discovery URLs and what
 * `KeyringTokenStore` uses to key keychain entries.
 *
 * Rules (per RFC 3986 §6.2 URI comparison):
 * - Trailing slashes stripped from the path.
 * - Scheme and authority (host + optional port) lowercased — both are
 *   case-insensitive per the RFC.
 * - Default ports (80 for http, 443 for https) collapsed via `URL.host`.
 * - Path preserved case-sensitively.
 * - Query string and fragment dropped: OIDC issuers are defined by
 *   scheme + authority + path, and carrying them through would break
 *   downstream path concatenation (e.g. appending
 *   `/.well-known/openid-configuration`).
 *
 * If the input is not a parseable URL, the function trims trailing
 * slashes and returns — discovery will surface a clearer error than
 * this function could.
 */
export declare function normalizeIssuerURL(url: string): string;