Broker conformance test: Control plane

[grantr]

Problem
We need a conformance test of the Broker control plane specification.

Persona:
Contributor

Exit Criteria
A conformance test that produces a conformant/non-conformant result and can be applied to any Broker implementation.

Time Estimate (optional):
1w

Additional context (optional)
#2306

A single test sequence can verify all control plane characteristics:

1. Trigger can be created before Broker (with attributes filter)
2. Broker can be created and progresses to Ready
3. Ready Broker is Addressable
4. Trigger with Ready broker progresses to Ready
5. Ready Trigger includes status.subscriberUri

/area test-and-release
/label proposal/0.14

[grantr]

/assign grantr
/unassign liu-cong