Maven virtual registry: multiple registries

🔥 Problem

In Maven virtual registry MVC (API only interactions) (&14137 - closed) • David Fernandez, Moaz Khalifa • 18.1, we started the implementation with the following constraint: only one top-level group can have a maven virtual registry.

We're now at the point where we can lift this constraint.

🚒 Solution

• Bump the 1 maven registry limit to a higher limit (to be discussed).
• Update the database / backend to apply the new constraint.
• Verify that the list maven registries Rest API endpoint is behaving as expected, with pagination.