Error inserting code

Hello,

I am trying to insert a whole code to manage a reservation, and when I save, the content is deleted. I have tried with different options and all of them are deleted when saving the changes.

How can we put this code so that it is not deleted?

The problem comes mainly with the <template

<template id="don-EDCFD2BC-EE8E-4D29-A680-25474C872D85" donref="2e2f55d7-227c-4264-8e79-06b37480fec0" donlocale="ES"></template>

<script type="text/javascript" src="https://service.donicus.com/dist/loader.min.js" donname="donicusBooking"></script>

The page I need help with: [log in to see the link]