API v2 - v2 systems_controller and systems actions

* `Api::V2::SystemsController` extends `Api::V2::ApiController` instead
  of `Api::V1::SystemsController` so if a v2 action doesn't work, try
  the v1 action for now.
* moved a common method from `SystemsController` to `ApiController`
* fixed some indentations

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- [x] fix broken tests