curl --request GET \
  --url https://api-v2.missioninbox.com/billing/check_grace_period_status/ \
  --header 'Authorization: Basic <encoded-value>'

{
  "user_status": "<string>",
  "action_taken": "<string>",
  "message": "<string>",
  "days_since_cancellation": 123,
  "days_remaining_in_grace_period": 123,
  "grace_period_ends": "<string>"
}