Hi Eduardo
Although you can insert an HTML snippet in InDesign this is a long way off being able to embed a full website as you describe. What you want is not going to be possible inside any regular EPUB reader, I’m afraid.
My company’s software CircularFLO https://www.circularflo.com allows for the placing of more complex web code such as Hype animations and puzzle widgets etc. but this is still a way off adding a complex website that would need to communicate outside of the EPUB to make purchases
Technically speaking the EPUB standard stipulates that all content must be inside the EPUB and so available when offline. There are some edge cases where streaming of video can be possible for instance and I have recently been involved in a project that linked out to Spotify playlists.
The only other solution is to take your EPUB onto the web in a EPUB reader like Readium Cloud Reader. We currently use this with our MasterPlan LIVE software e.g. https://www.galdosgift.com/book-sample?mp=Client3333/Job9781999857608/002 but by then you are in a browser and on the web and so for your project you would probably just want to link to the client’s website at this point?
Hope this helps
Ken Jones
Circular Software
https://www.circularsoftware.com
.
