code: public String resolve(final String rel) {
          final Optional<CuriTemplate> curiTemplate = matchingCuriTemplateFor(curies, rel);
          return curiTemplate.map(t -> t.curiedRelFrom(rel)).orElse(rel);
      }
docs: Resolves a link-relation type (curied or full rel) and returns the curied form, or
  the unchanged rel, if no matching CURI is registered.
  
  @param rel link-relation type
  @return curied link-relation type