POST /getUnusedLinkedInPost

• Auth: header x-api-key: <API_KEY>
• Body: { businessId: string } (required)
• Behavior: returns one LinkedIn post where used == false and exclude == false.
• Responses:
  • 200: { id, data }
  • 400: missing businessId
  • 403: invalid API key
  • 404: when none available
  • 500: internal error

Source: apps/functions/getUnusedLinkedInPost.js.