Nested attribute population strategies

[dushky]

Extend functionality for nested attributes of already nested attribute.
In this example, the strategy for form_sections is called properly, but section_components is not. It is a strategy that is defined in related model form_sections.

{
  "form_sections": [
    {
      "id": "31ab9129-3ced-4f36-a960-c2429f5fd853",
      "section_components": [
        {
          "id": "ad47882e-a56a-4366-86a4-239abce0b6c9",
          "name": "section component 1"
        },
        {
          "id": "ad47882e-a56a-4366-86a4-239abce0b6c9",
          "name": "section component 2"
        }
      ]
    }
  ]
}