curl --request POST \
  --url http://localhost:8000/api/v1/subscriptions/assign \
  --header 'Authorization: Bearer <token>' \
  --header 'Content-Type: application/json' \
  --data '
{
  "google_ads_customer_id": 123,
  "subscription_plan_id": 123,
  "starts_at": "2023-11-07T05:31:56Z",
  "expires_at": "2023-11-07T05:31:56Z"
}
'

{
  "google_ads_customer_id": 123,
  "subscription_plan_id": 123,
  "starts_at": "2023-11-07T05:31:56Z",
  "expires_at": "2023-11-07T05:31:56Z",
  "id": 123,
  "date_added": "2023-11-07T05:31:56Z",
  "date_updated": "2023-11-07T05:31:56Z",
  "cancelled_at": "2023-11-07T05:31:56Z"
}