async function favoritePost(req, res, next) {
  try {
    const user = await User.findById(req.user._id);
    await user._favorites.posts(req.params.id);
    return res.sendStatus(HTTPStatus.OK);
  } catch (err) {
    err.status = HTTPStatus.BAD_REQUEST;
    return next(err);
  }
}
@api {post} /posts/:id/favorite Favorite a post
@apiDescription Favorite a post or unfavorite if already.
@apiName favoritePost
@apiGroup Post

@apiHeader {Authorization} Authorization JWT Token

@apiParam {String} id Post unique ID.

@apiSuccess {Number} status Status of the Request.

@apiParam (Login) {String} pass Only logged in users can do this.

@apiHeaderExample {json} Header-Example:
{
 "AUTHORIZATION": "JWT eyJhbGciOiJIUzI1NiIsInR5cCI6IkpXVCJ9.eyJfaWQiOiI1OTBhMWI3ODAzMDI3N2NiNjQxM2JhZGUiLCJpYXQiOjE0OTM4MzQ2MTZ9.RSlMF6RRwAALZQRdfKrOZWnuHBk-mQNnRcCLJsc8zio"
}

@apiSuccessExample Success-Response:

HTTP/1.1 200 OK

@apiErrorExample {json} Post not found
   HTTP/1.1 404 Not Found
@apiErrorExample {json} Unauthorized
   HTTP/1.1 401 Unauthorized