ExternalMessage Plugin API
===========================

POST /message
  Headers: X-API-Key: your-api-key (if API key required)
  Content-Type: application/json
  Body: { "source": "discord", "sender": "username", "message": "Hello!" }
  
  Or with API key in body:
  Body: { "source": "letta", "message": "Hi!", "api_key": "your-key" }

  Or query param:
  POST /message?api_key=your-key
  
GET /status
  Returns plugin status and message count

GET /
  This help message

API Key Required: True
Port: 18721