code: protected HalRepresentation withEmbedded(final String rel, final HalRepresentation embeddedItem) {
          embedded = copyOf(embedded).with(rel, embeddedItem).using(curies).build();
          return this;
      }
docs: Adds an embedded item for a link-relation type to the HalRepresentation.
  <p>
  The embedded item will be rendered as a single resource object.
  </p>
  <p>
  If {@code rel} is already present, it is replaced by the new embedded items.
  </p>
  
  @param rel the link-relation type of the embedded item that is added or replaced
  @param embeddedItem the new value for the specified link-relation type
  @return this
  
  @since 2.0.0