POST /getParticipants

• Auth: header x-api-key: <API_KEY>
• Body: { businessId: string } (required)
• Behavior: returns onboarded participants in businesses/{businessId}/participants where isOnboarded == true.
• Responses:
  • 200: [] or array of participants
  • 400: missing businessId
  • 403: invalid API key
  • 500: internal error

Source: apps/functions/getParticipants.js.