Suggestion: Collect builders and config annotations into main interfaces

[aguibert]

Currently MP Concurrency has the pattern of 3 classes per object:

• core interface (e.g. ManagedExecutor)
• config annotation (e.g. @ManagedExecutorConfig)
• builder interface (e.g. ManagedExecutorBuilder)

To make it a bit more obvious that these objects go together, I propose that we collect the config annotation and builder interface into the core interface as inner-classes, like this:

// Single import statement for core, config, and builder
import org.eclipse.microprofile.concurrent.ManagedExecutor;

public class MyBean {
    @Inject
    @ManagedExecutor.Config(maxAsync = 5)
    public ManagedExecutor ex;
    
    @Produces
    public ManagedExecutor defaultExec() {
    		return ManagedExecutor.Builder.instance()
    			.maxAsync(5)
    			.build();
    }
}

[njr-11]

Thanks for the suggestion. In general this is a good idea, but the CDI qualifier annotation @ManagedExecutorConfig will soon end up with a dependency on CDI (which isn't there currently, but it is being fixed in another pull) and this proposal would result in the MP Concurrency spec having a main path dependency on CDI, which we are trying to avoid.

[njr-11]

My comment above no longer applies. We will not be using Qualifier. However @ManagedExecutor.Config looks awkward. Moving the builder under ManageedExecutor does seem reasonable.

[manovotn]

I think moving the build class as an inner class is good idea as it makes it easier to use, +1 for that.
But I would keep the annotation as a separate class.