New settings variable

I propose to add a new variable in the settings: PREVIEW_HOST

Currently preview host is hardcoded to preview.LMS_HOST, which may be difficult to manage if we’re using a different subdomain. By adding the new variable, we can easily change the preview domain name.

I agree that the preview domain should not be hardcoded. Would you like to do the change yourself? If not I can take care of it.
Note that the preview domain must be a subdomain of the LMS, and this information should be added to the docs.

I can PR. But I’m not sure where does the docs mention that preview domain must be a subdomain of the LMS. In fact, my preview domain is not a subdomain of LMS and it’s still working fine.

Sounds good! Looking forward to your PR.

Really? I must have misremembered. Let’s not add this instruction to the PR, then.