code: public final Post withAuthor(final User user) {
        return new Post(id, slug, title, excerpt, content, authorId, user,
                publishTimestamp, modifiedTimestamp, status, parentId,
                guid, commentCount, metadata, type, mimeType, taxonomyTerms, children);
     }
docs: Adds an author to a post.
  @param user The user that represents the author.
  @return The post with author added.