When switching to CDI first, #377, I would like deprecate the existing PersistenceContext/PersistenceUnit uses @Named or @Qualifier with @Inject instead.

@Inject @Named("customerDatabase")  EntityManager em;
@Inject @CustomerDatabase  EntityManager em;

@Inject @CustomerDatabase  EntityManagerFactory emf;

@Qualifier is preferred, declaring an EMF with the same qualifiers, see #358