I want to embed a HTTPS website in another HTTPS website. They are hosted at different places and under different domains and their certs are issued for their respective domains.
How can I make sure the embedded website is only available through the embedding website and not directly?
Shall I use an iFrame or something else?
Can HTTPS and certs become a problem in this constellation?
Clarification:
So the embedded site is an appointment booking tool written in vue.js. It should be integrated into the embedding site, that is including it's header and footer. There are no links on the embedded site, only the vue.js app. The user is to book an appointment and be done with it. I want the user to not notice the tool is coming from an external source. SEO is completely irrelevant. In fact, I don't want anybody opening the tool other than through the embedding site.