Ember Cli Mirage: Active Model Adapter with JSONAPISerializer

I am on halfway of implementing JSON API structure (with underscore attributes).

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Actual state for development environment is:

I use the Active Model Adapter structure for requesting to the backend for resources and backend response me with JSON API structure.

In Application Serializer I am using JSONAPISerializer. I override methods:

serializeBelongsTo
keyForRelationship
keyForAttribute
serialize
serializeAttribute
serializeHasMany

and for development, everything works for me (backend in Rails communicate with Ember very good).

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The problem is with Ember CLI Mirage and conventions (not sure if there are simple solutions or I need to override again methods in this addon).

Actual state with Ember Cli Mirage and test environment:

I am using import { JSONAPISerializer } from 'ember-cli-mirage'; and then trying to manipulate proper request and then transform it for JSON API format.

It could work like this:

Ember Adapter (Active Model Adapter format - with underscore attributes) ---> Mirage Serializer should get request (find resources created before in tests with associations) and then response it with JSON API format ---> JSON API Serializer could catch it and fill Ember DS.

For now, I have a missing part to serialize it for all cases to JSON API standard (with underscored attributes)

Where should I do this transformation to minimize overriding JSONAPISerializer Mirage Serializer.

I noticed that there are some helpers, but I have a problem to wrap this knowledge together (http://www.ember-cli-mirage.com/docs/advanced/route-handlers#helpers)