I would like Cloudflare to send the HSTS header on the main domain, and on the
www subdomain, but not the other subdomains.
However I can only enable HSTS for the primary domain (and add
includesubdomains, which I can't use because I don't want HSTS enabled on all of them).
So I thought: maybe a page rule is the solution! But I can neither see a HSTS page rule, nor can I see a page rule category to add HTTP response header.
How do I do this? Am I missing something / am I blind? Or is this not possible with Cloudflare, and I have to do it on the host?