Exactly one of this annotation is needed in each Concern. It will be populated with the reference to the next Concern in the Invocation Stack or to the underlying Mixin instance if it is the last Modifier in the Invocation Stack.
If there is no @ConcernFor annotation on any of the member fields of a Modifier, or if there are more than one member field annotated with this annotation, then there will be a RuntimeException thrown.
NOTE: The @ConcernFor annotation should typically not be used. Instead, extend the class ConcernOf<mixintype> for effectively the same thing.
