@Override
    public Authenticator validateConfig(Map<String, String> config) {
        Objects.requireNonNull(config.get("username"), "must provide username.");
        Objects.requireNonNull(config.get("password"), "must provide password.");
        return this;
    }
Set BASIC auth credentials.

<ul>
  <li>username: username</li>
  <li>password: password</li>
</ul>

@author Marc Savy {@literal <marc@rhymewithgravy.com>}
gateway/engine/vertx-polling/src/main/java/io/apiman/gateway/engine/vertx/polling/fetchers/auth/BasicAuth.java