curl --request POST \
  --url https://{appid}.api-{region}.cometchat.io/v3/messages/{id}/reactions/{reaction} \
  --header 'apikey: <api-key>' \
  --header 'onBehalfOf: <onbehalfof>'

{
  "data": {
    "id": "2",
    "conversationId": "superhero1_user_superhero2",
    "sender": "superhero1",
    "receiverType": "user",
    "receiver": "superhero2",
    "category": "message",
    "type": "text",
    "data": {
      "text": "Hi,",
      "entities": {
        "sender": {
          "entity": {
            "uid": "superhero1",
            "name": "Iron Man",
            "role": "default",
            "status": "offline"
          },
          "entityType": "user"
        },
        "receiver": {
          "entity": {
            "uid": "superhero2",
            "name": "Captain America",
            "role": "default",
            "status": "offline",
            "conversationId": "superhero1_user_superhero2"
          },
          "entityType": "user"
        }
      },
      "reactions": [
        {
          "reaction": ":reaction",
          "count": 1
        },
        {
          "reaction": "😅",
          "count": 1
        },
        {
          "reaction": "😒",
          "count": 1,
          "reactedByMe": true
        },
        {
          "reaction": "🤨",
          "count": 1,
          "reactedByMe": true
        }
      ]
    },
    "sentAt": 1700210266,
    "updatedAt": 1700210266
  }
}