@UnstableApi
    public ServerBuilder addHeaders(
            Iterable<? extends Entry<? extends CharSequence, ?>> defaultHeaders) {
        virtualHostTemplate.addHeaders(defaultHeaders);
        return this;
    }
Adds the default HTTP headers for an {@link HttpResponse} served by the default {@link VirtualHost}.

<p>Note that the default headers could be overridden if the same {@link HttpHeaderNames} are defined in
one of the followings:
<ul>
  <li>{@link ServiceRequestContext#additionalResponseHeaders()}</li>
  <li>The {@link ResponseHeaders} of the {@link HttpResponse}</li>
  <li>{@link VirtualHostBuilder#addHeaders(Iterable)}</li>
  <li>{@link VirtualHostServiceBindingBuilder#addHeaders(Iterable)} or
      {@link VirtualHostAnnotatedServiceBindingBuilder#addHeaders(Iterable)}</li>
</ul>
core/src/main/java/com/linecorp/armeria/server/ServerBuilder.java