code: protected <X extends Comparable<? super X>> Specification<ENTITY> buildRangeSpecification(RangeFilter<X> filter,
                                                                                                SingularAttribute<? super ENTITY, X> field) {
          return buildSpecification(filter, root -> root.get(field));
      }
docs: Helper function to return a specification for filtering on a single {@link Comparable}, where equality, less
  than, greater than and less-than-or-equal-to and greater-than-or-equal-to and null/non-null conditions are
  supported.
  
  @param filter the individual attribute filter coming from the frontend.
  @param field  the JPA static metamodel representing the field.
  @param <X>    The type of the attribute which is filtered.
  @return a Specification