Implement per-route options in BBS

[maxmoehl]

Proposed Change

In RFC0027 Generic Per-Route Features we decided to implement a new field for routes which can contain additional, custom configuration for a route. Together with this new feature we also want to implement the first property making use of it: customisable load balancing algorithms.

This new field must be implemented in BBS to allow cloud controller to forward the new field and for route-emitter to announce it via nats. The field should be opaque to BBS, for BBS it is a string which can contain arbitrary data.

Acceptance criteria

• BBS endpoints are adjusted to accept the new field.
• BBS stores the new field of routes.

Related links

• RFC tracking issue: [RFC0027] Generic Per-Route Features community#909