Create HTTP Endpoint for View modes/content templates

My preference would be the first way (not flat). And yes the frontend can construct the 'layout_url' => '/xb/api/v0/layout-template/node/page/full/ given the response.

$view_modes = [
      'node' => [
        'page' => [
          'full' => [
            // Whether template has auto-save changes. This can be tru even if
            // existing_template is false since we auto-save templates before
            // first publishing without creating a new saved template.
            'auto-save-changes' => TRUE,
            // Where the there is an existing template saved.
            'existing_template' => TRUE,
            // The ID does require an exisitng template because it is based on
            // entity props that can't be changed.
            'template_id' => 'node.page.full',
          ]
          'teaser' => [
            'auto-save-changes' => FALSE,
            'existing_template' => FALSE,
            'template_id' => 'node.teaser.full',
          ]
        ]
        'article' => [
          'full' => [
            'auto-save-changes' => FALSE,
            'existing_template' => TRUE,
            'template_id' => 'node.article.page',
          ]
          'teaser' => [
            'auto-save-changes' => TRUE,
            'existing_template' => TRUE,
            'template_id' => 'node.article.teaser',
          ]
        ]
      ],
    ];

The issue summary already talks about nodes only, but I just wanted to reinforce that at this stage we're only targeting node bundles, no other entity types are in scope.

The issue summary already talks about nodes only, but I just wanted to reinforce that at this stage we're only targeting node bundles, no other entity types are in scope.

FYI this is enforced since https://git.drupalcode.org/project/experience_builder/-/commit/843e7b0b1...