Improved check if content is not empty

[mikadamczyk]

🎫 Issue	IBX-XXXXX

Description:

We cannot move the “has content” check for the content block into the PHP side of a Symfony UX Twig Component, because the component class has no access to the rendered output of Twig blocks/slots. Blocks are resolved only during template rendering, so from PHP, you cannot reliably know if the content slot is empty or not.

We will keep the check in Twig, but avoid repeated block('content') calls by buffering the block once into a variable.

{% set _content %}{% block content %}{% endblock %}{% endset %}
{% set has_content = _content|striptags|trim is not empty %}

This way _content can be reused wherever needed, and has_content gives a clean boolean to control conditional rendering. If further centralization is desired, a small Twig filter/test or a helper method can process _content, but the capture of the block itself must remain in Twig.

For QA:

Documentation: