It is possible to force to add "http" or "https" ahead of the canonical URL (to avoid copy concerning the http and https version of a web site). Ex: if you end up picking to power https for your canonical URL, the canonical URL from the website page might be https://addons.prestashop.com/nl/seo-zoekmachineoptimalisatie-vermelding/31857-automatische-google-rich-snippets-json-ld-opengraph-seo.html