Ember Data Model Nesting/Namespacing

One thing I stumbled upon when trying Ember Data is the seemingly lack of support for namespaced data models. Running `ember generate model user/google` generates a UserGoogle model in `app/models/user/google.js`.

However, the issue is that Ember Data itself does not seem to support namespaced model names. I assume the [JSON API spec](https://jsonapi.org/format/#document-member-names) does not allow `/` in the [resource `type`](https://jsonapi.org/format/#document-resource-object-identification), so Ember Data assumes no model will ever be namespaced. When trying to do Ember Data operations like finding a specific resource, Ember Data seems to error out trying to load the class.

When using the same code but doing `ember generate model userGoogle`, the code works. It generates files like `app/models/user-google.js`.

I think a note should be added to the guides if there is indeed a limitation with namespaced Ember Data model names. I assumed that model namespaces would be supported because routes and components support namespaces.