@Override
  public HttpResponse execute(ClientRequestContext ctx, HttpRequest req) throws Exception {
    String credentials = basicCredentials.getCredentials();
    if (credentials != null) {
      ctx.addAdditionalRequestHeader(HttpHeaderNames.AUTHORIZATION, credentials);
    }
    return unwrap().execute(ctx, req);
  }
Adds basic auth username and password to every request.

<p>Ref: <a href="https://www.elastic.co/guide/en/x-pack/current/how-security-works.html"> How
Elasticsearch security works</a></p>
zipkin-server/src/main/java/zipkin2/server/internal/elasticsearch/BasicAuthInterceptor.java