Validate subscription exists before starting an endpoint

[SzymonPobiega]

Describe the feature.

Is your feature related to a problem? Please describe.

In a more strictly controlled environments might not be possible to run endpoints with high enough privileges to take advantage of the auto subscribe feature of NServiceBus that ensures subscription exist before a subscriber endpoint starts up.

In these environments subscriptions are usually managed by some kind of deployment scripts that need to run before the endpoint starts up. This creates a danger that, should these scripts be incomplete or someone forgot to run them, an endpoint might miss events it is supposed to be subscribed to.

Describe the requested feature

The subscription validation feature would make sure that when a subscriber endpoint starts up, all relevant subscriptions are present.

Potential solution ideas

• Use broker's SDK at the endpoint level to validate subscriptions exist -- this might cause issues in some brokers e.g. Azure Service Bus which require full manage rights to check existence of entities (queues, topics and subscriptions)
• Use heuristics e.g. log warning when no event of a given type is received while other events are flowing
• Use a centralized component (that is running in context of account with elevated privileges) to manage event routing topology

Additional Context

No response