Promote to chain environment

curl --request POST \
--url https://api.baseten.co/v1/chains/{chain_id}/environments/{env_name}/promote \
--header "Authorization: Bearer $BASETEN_API_KEY" \
--data '{
  "scale_down_previous_deployment": true,
  "deployment_id": null
}'

{
  "id": "<string>",
  "created_at": "2023-11-07T05:31:56Z",
  "chain_id": "<string>",
  "environment": "<string>",
  "chainlets": [
    {
      "id": "<string>",
      "name": "<string>",
      "autoscaling_settings": {
        "min_replica": 123,
        "max_replica": 123,
        "autoscaling_window": 123,
        "scale_down_delay": 123,
        "concurrency_target": 123,
        "target_utilization_percentage": 123,
        "target_in_flight_tokens": 123,
        "max_scale_down_rate": 123
      },
      "instance_type_name": "<string>",
      "active_replica_count": 123
    }
  ]
}