Have you ever encountered this error while working on
`DEPRECATION WARNING: In XXX class you exposed a `has_one` relationship using the `belongs_to` class method. We think `has_one` is more appropriate. If you know what you’re doing, and don’t want to see this warning again, override the `belongs_to` class method on your resource.
If yes this post is for you. Dont break your heads its on `jsonapi-resources`.
It looks like jsoapi-resources did not implement the `belongs_to` as how it should be. At least as of this writing (0.9.0v). It treats `belongs_to` and `has_one` relations in the way. here is the source which points to this. So for time being change your `belongs_to` to `has_one` and you are gold. Happy coding!