usernamePasswordAuthenticator
import { usernamePasswordAuthenticator } from "https://raw.githubusercontent.com/nats-io/nats.deno/v1.28.2/nats-base-client/internal_mod.ts";
Returns a user/pass authenticator for the specified user and optional password
function usernamePasswordAuthenticator(user: string | (() => string), pass?: string | (() => string)): Authenticator;