How do I render content "as is" from custom controller

Question

I've created a custom controller that pulls content from another node (the body). That content is defined in the node as Raw HTML.

  public function page(Request $request): array {

    $nid = $request->attributes->get('_nid');
    $node_storage = $this->entityTypeManager()->getStorage('node');
    $node = $node_storage->load($nid);
    $content = $node->get('field_content')->value;

    // Load Entity using passed NID from key.
    $build = $content;
    // Return new Response($build);
    $render_array['snippet'] = [
      '#theme' => 'webpart_snippet',
      '#content' => $build,
      '#prefix' => '<div class="webpart_outer_wrapper">',
      '#suffix' => '</div>',
    ];
    return $render_array;

  }

I would like to render that content as if it were a native Symfony response. (e.g., correctly parse and HTML tags AND scripts)

In the node that I'm pulling in, I have, for example

<h1>This is text</h1> 

and that is exactly what is showing on the page

It should be

This is text

I have defined a custom theme as well as twig template

/**
 * Implements hook_theme().
 * Declare a new theme
 */
function custom_webpart_snippet_theme() {
  return [
    'webpart_snippet' => [
      'variables' => [
        'content' => '',
      ],
    ],
  ];
}

Answer 1

Since this is a text area field, you need to specify a type of render element, processed_text.

$render_array['snippet'] = [
  '#theme' => 'webpart_snippet',
  '#type' => 'processed_text',
  '#text' => $node->field_content->value,
  '#format' => $node->field_content->format,
  '#prefix' => '<div class="webpart_outer_wrapper">',
  '#suffix' => '</div>',
];

Answer 2

The problem was in the template (twig) Simply the raw filter see doc description here

Non-working code

<div class="snippet-wrapper">
  <div>{{ content }}</div>
</div>

Working code

<div class="snippet-wrapper">
  <div>{{ content | raw }}</div>
</div>