Convert node URL to absolute

We are using Drupal Core v8.6.2 and we have a url variable in our node--page.html.twig template. While using ksm() and {{ kint() }} we are finding that if we use hook_preproces_node($ variables) that the url is inserted into the $ variables array. Unfortunately this url is relative, but we need an absolute URL in our twig template.

How can we convert this url variable from our node--page.html.twig template to be absolute?

node--page.html.twig

I have reduced the comments section to only include comments that were relevant to the question.

{# /**  * @file  * Theme override to display a node.  *  * Available variables:  * - node: The node entity with limited access to object properties and methods.  * - label: The title of the node.  * - content: All node items. Use {{ content }} to print them all,  * - url: Direct URL of the current node.  * - attributes: HTML attributes for the containing element.  * @see template_preprocess_node()  *  */ #}  <a href="{{ url }}> {# url is the variable we want to be absolute #}   <h2> {{ label }} </h2>   {{ content.body }} </a>