thinky hasAndBelongsToMany

controller.js

ctrl.post = function *(next){
  var data = this.request.body;

  var tagIds = data.tags.map(tag => {
    return tag.id;
  });

  delete data.tags;

  var post = new Post(data);

  post.tags = tagIds;

  var newPost = yield post.saveAll(); //save joins
  var result = yield Post.get(newPost.id).getJoin({ tags: true });

  this.body = result;

  yield next;
};