Configuration hierarchy controller

This MR should add the controller for the mounting-actions defined here: https://notes.desy.de/OpCZ8SOGSMyzCJ5BkpBvfA

GET /backend/api/v1/controller/configurations/<configuration-id>/mounting-actions?timepoint=<time-point>
Response:
[{
  "action": {
    "id": "1",
    "type": "platform_mount_action",
    "attributes": {
      "offset_y": 0.0,
      "description": "",
      "offset_x": 0.0,
      "updated_at": null,
      "offset_z": 0.0,
      "begin_date": "2022-04-11T12:08:13.000000"
    }
  },
  "entity": {
    "id": "2",
    "type": "platform",
    "attributes": {
      "short_name": "platform_x"
    }
  },
  "children": [
    {
      "aktion": {
        "id": "4",
        "type": "",
        "attrbiutes": {}
      },
      "entity": {
        "id": "",
        "type": "",
        "attributes": {}
      },
      "children": []
    }
  ]
}]