Create a capacity investment on an epic

{
  "capacity_investment": {
    "date_source": "manual_dates",
    "start_date": "2019-01-01",
    "end_date": "2019-01-01"
  }
}

{
  "capacity_investment": {
    "id": "6776881149484188557",
    "capacity_scenario_id": "997808419",
    "total": 0,
    "estimate_source": "epics",
    "date_source": "manual_dates",
    "start_date": "2019-01-01",
    "end_date": "2019-01-01",
    "initiative": {
      "id": "1042392694",
      "name": "Workspace line initiative 1",
      "reference_num": "PL1-S-1",
      "created_at": "2019-01-01T00:00:00.000Z",
      "url": "https://company.aha.io/initiatives/PL1-S-1",
      "resource": "https://company.aha.io/api/v1/initiatives/PL1-S-1"
    },
    "estimate_values": [
      {
        "id": "6776881149486881903",
        "team_id": null,
        "team_membership_id": null,
        "period_start": null,
        "total": 0,
        "computed": true,
        "ignored": false
      }
    ],
    "custom_fields": []
  }
}