Improve @ConditionalOnEnabledEndpoint to be used on any component

[snicoll]

If a component is solely used in the context of an endpoint, there is no easy way to make it available only said component is enabled. The main reason behind that is that the logic in @ConditionalOnEnabledEndpoint requires the return type to be an endpoint (or an extension).

[snicoll]

I've a proposal in 0d96b2a that complexifies the API a bit. It also opens a case that would lead to a very weird scenario:

@Bean
@ConditionalOnEnabledEndpoint(endpoint = MyOtherEndpoint.class)
public MyEndpoint myEndpoint() { ... }

The sample above would ignore management.endpoint.my.enabled and only rely on management.endpoint.myother.enabled.

Also, the annotation attribute defaulting to Endpoint is weird (perhaps Object would be better ?)

[philwebb]

I quite like Void.class for class defaults that aren't considered.

[philwebb]

I think the change is sensible and I'm not too worried about the scenario you mentioned above.