Get channel participants

curl --request GET \
  --url http://localhost:3000/api/messaging/central-channels/{channelId}/participants

{
  "success": true,
  "data": [
    {
      "id": "3c90c3cc-0d44-4b50-8888-8dd25736052a",
      "userId": "3c90c3cc-0d44-4b50-8888-8dd25736052a",
      "name": "<string>",
      "role": "admin",
      "joinedAt": 123
    }
  ]
}