Create a collection of rooms from a template set on-the-fly

We are exploring using Mozilla Hubs for an immersive digital "book" (using our own hubs-cloud instance). We need to have each visitor have their own private sharable version of the interactive book, which they can "mark up" and invite others to visit (or not). So, each student in a class would have their own, each person who visits the site, etc. We do not want public shared versions.

To do this, we need to instantiate a collection of rooms for each person. The obvious solution is that each person who visits must log in, and when someone logs in the first time we generate the set of rooms for them.

No idea what the right approach is. One constraints is that the rooms will be linked together, perhaps in cycles, so that the new set of rooms must have the correct links.

My current thought is that this could be done by

* us creating a set of rooms as a template, linked together appropriately
* having the ability to say "create a copy of this set of rooms, updating hubs links in the rooms if the link is to another room in the set".

I have no idea if this can be done on the client side, or if it requires server-side features.

It feels like some of what is needed for this will also be needed for the export/import ideas? For example, if it was possible to import a set of rooms into a server, and the import was smart enough to deal with assets already loaded into the server (e.g., based on their URL) and links between rooms in the set, we could do this by creating rooms, exporting the set, and then importing the set for each new user.

┆Issue is synchronized with this [Jira Task](https://mozilla-hub.atlassian.net/browse/HUBS-1047)

The issue names no files, tests, or entry points. Start by determining whether room-set creation belongs on the client or server, then review the proposed export/import approach. Done means a template set can be copied for a user while preserving links between rooms and reusing already-loaded assets.

Written by the indexing model from the issue text.