In conf.py product_page doesn't take https:// even though the other links in html_context do.

In `conf.py`, `product_page` doesn't take `https://` even though the other links in `html_context` do.

This is bad UX and has also caused issues.

I suggest this field be made to accept a full URL just like the other fields (e.g., `discourse` or `mattermost`). For backward compatibility, maybe this could be handled conditionally, as in, if there is no `https://` add it etc.

Thanks!

Start in conf.py and inspect how product_page is handled alongside the other html_context links, especially discourse and mattermost. Update the handling so product_page accepts a full URL while preserving existing values without a scheme; done means both forms work consistently.

Written by the indexing model from the issue text.