Support for virtual keys

[heiko-braun]

It would be nice to have support for accessing models via virtual keys, generated from and managed by nexus.

Use cases

• Users can generate virtual keys for themselves
• These keys can be used to access models
• Keys can be revoked, or have a lifetime
• Other config settings can be attached to keys (i.e. which models to access, budgets, etc)

[linear]

GB-9525 Support for virtual keys

[pimeys]

This is one of the goals for sure. Let's get the basics done in the router first, and then focus on user management.