public Set<GRNDescriptor> getDescriptors(Collection<GRN> grns) {
        return grns.stream().map(this::getDescriptor).collect(Collectors.toSet());
    }
@Test
    void getDescriptors() {
        final ImmutableMap<GRNType, GRNDescriptorProvider> providers =  ImmutableMap.of(
                user.grnType(), grn -> GRNDescriptor.create(grn, "Jane Doe"),
                dashboard.grnType(), grn -> GRNDescriptor.create(grn, "A Dashboard")
        );
        final GRNDescriptorService service = new GRNDescriptorService(providers);

        final Set<GRNDescriptor> descriptors = service.getDescriptors(ImmutableSet.of(user, dashboard));

        assertThat(descriptors).containsExactlyInAnyOrder(
                GRNDescriptor.create(GRNTypes.USER.toGRN("jane"), "Jane Doe"),
                GRNDescriptor.create(GRNTypes.DASHBOARD.toGRN("abc123"), "A Dashboard")
        );
    }