code: public static Builder builder(final Resource r) {
          return builder(r.getIdentifier()).interactionModel(r.getInteractionModel())
                          .container(r.getContainer().orElse(null))
                          .memberRelation(r.getMemberRelation().orElse(null))
                          .membershipResource(r.getMembershipResource().orElse(null))
                          .memberOfRelation(r.getMemberOfRelation().orElse(null))
                          .insertedContentRelation(r.getInsertedContentRelation().orElse(null));
      }
docs: A mutable builder for a {@link Metadata} object.
  
  @param r the resource
  @return a builder for a {@link Metadata} object