Constructs incorrect query when gathering a collection that contains a single object.

[abepetrillo]

Given an ember model:

export default DS.Model.extend({
resources: DS.hasMany('resources', async: true)
});

In the case where resources is [1], the adapter assumes that the graphql api has the singular type available, and you can end up getting an error similar to:

    {"0"=>"Field 'resource' doesn't exist on type 'Query'"}

This means that to make this workable, you need to make sure the API has both the singular and plural way of accessing the resource which can be quite verbose.

[Arkham]

The implementation follows closely the defaults of the other ember data serializers, so for example in the case of REST and AMS serializers it will attempt to access the 'show' endpoint when the associated resource is singular and it will access the 'index' endpoint only when there are multiple associated resources.

[daemonsy]

This might be solveable by implementing the node interface of GraphQL where any object can be globally fetched. Will be looking into this