Get upcoming credit grant applications

curl --request GET \
  --url https://api.cloud.flexprice.io/v1/subscriptions/{id}/grants/upcoming \
  --header 'x-api-key: <api-key>'

{
  "items": [
    {
      "application_reason": "first_time_recurring_credit_grant",
      "application_status": "applied",
      "applied_at": "<string>",
      "created_at": "<string>",
      "created_by": "<string>",
      "credit_grant_id": "<string>",
      "credits": 123,
      "environment_id": "<string>",
      "failure_reason": "<string>",
      "id": "<string>",
      "idempotency_key": "<string>",
      "metadata": {},
      "period_end": "<string>",
      "period_start": "<string>",
      "retry_count": 123,
      "scheduled_for": "<string>",
      "status": "published",
      "subscription_id": "<string>",
      "subscription_status_at_application": "active",
      "tenant_id": "<string>",
      "updated_at": "<string>",
      "updated_by": "<string>"
    }
  ],
  "pagination": {
    "limit": 123,
    "offset": 123,
    "total": 123
  }
}