XF 1.5 Serve the header & footer + user info round pages on a different domain?

[Stuart Wright]

So I'm wanting to integrate with a white label resource which has to be on a different website. We will be able to set up domains like broadband.avforums.com for this resource.
I want to create an integration which is as seamless as possible.
Which means serving our header and footer round the content.
How hard is it to have cookies retained so logged-in users are still logged in when they visit this other site?
And then serve the header and footer the same as it would be served to users & guests visiting normally?
Is is possible?

 

[Jake Bunce]

You want the last example in this post to open up your cookie scope:

https://xenforo.com/community/threads/xenforos-handing-of-cookie-domains.15260/#post-200173

But switching cookie domains may cause weirdness with both the new and old cookies in existence. When changing the cookie domain it is usually best to change the prefix as well to invalidate all old cookies to prevent conflict, but then of course everyone will need to login again.

Kotomi was the goto for quick and easy XF integration back in the day:

https://xenforo.com/community/resources/kotomi-generic-script-bridge.122/

...but it's old and will need its front controller updated at the very least.