MilestoneStartedevent type

Milestone transitioned Planned -> In Flight.

Full spec

{
  "name": "MilestoneStarted",
  "description": "Milestone transitioned Planned -> In Flight.",
  "current_version": 1,
  "actor_type_allowed": [
    "human"
  ],
  "object_type": "Milestone",
  "payload_versions": {
    "v1": {
      "type": "object",
      "additionalProperties": false,
      "required": [
        "milestone_id",
        "started_by"
      ],
      "properties": {
        "milestone_id": {
          "type": "string",
          "format": "uuid"
        },
        "started_by": {
          "type": "string",
          "format": "uuid"
        },
        "actual_start_date": {
          "type": "string",
          "format": "date"
        }
      }
    }
  },
  "projections_consuming": [
    "milestones_view",
    "timeline_view",
    "audit_log"
  ],
  "canonicalizer_module": "event-canonicalizers/milestone_started.ts"
}