Leveraging the power of NoSQL

So far, our MongoEngine code should look like the following:

available_roles = ('admin', 'poster', 'default')

class User(mongo.Document):
    username = mongo.StringField(required=True)
    password = mongo.StringField(required=True)
    roles = mongo.ListField(
        mongo.StringField(choices=available_roles)
    )

    def __repr__(self):
        return '<User {}>'.format(self.username)


class Comment(mongo.EmbeddedDocument):
    name = mongo.StringField(required=True)
    text = mongo.StringField(required=True)
    date = mongo.DateTimeField(
        default=datetime.datetime.now()
    )

    def __repr__(self):
        return "<Comment '{}'>".format(self.text[:15])


class Post(mongo.Document):
    title = mongo.StringField(required=True)
    text = mongo.StringField()
    publish_date = mongo.DateTimeField(
        default=datetime.datetime.now()
    )
    user = mongo.ReferenceField(User)
    comments = mongo.ListField(
        mongo.EmbeddedDocumentField...