curl --request POST \
  --url https://api.firma.dev/functions/v1/signing-request-api/workspaces/{id}/api-key/regenerate \
  --header 'Authorization: <api-key>'

{
  "new_key": {
    "api_key": "firma_abc123xyz...",
    "created_at": "2024-12-17T10:30:00Z"
  },
  "expiring_keys": [
    {
      "id": "old-key-uuid",
      "api_key": "firma_old456...",
      "expires_at": "2024-12-18T10:30:00Z"
    }
  ],
  "workspace_id": "123e4567-e89b-12d3-a456-426614174000"
}