template.json

{
  "type": "message",
  "attachments": [
    {
      "contentType": "application/vnd.microsoft.card.adaptive",
      "contentUrl": null,
      "content": {
        "type": "AdaptiveCard",
        "body": [
          {
            "type": "ColumnSet",
            "columns": [
              {
                "type": "Column",
                "items": [
                  {
                    "type": "Image",
                    "style": "Person",
                    "url": "{{ data.pullrequest.author.links.avatar.href }}",
                    "altText": "{{ data.pullrequest.author.display_name }}",
                    "size": "Small"
                  }
                ],
                "width": "auto"
              },
              {
                "type": "Column",
                "items": [
                  {
                    "type": "TextBlock",
                    "weight": "Bolder",
                    "text": "{{ data.pullrequest.author.display_name }}",
                    "wrap": true
                  },
                  {
                    "type": "TextBlock",
                    "spacing": "None",
                    "text": "Created a pull request",
                    "isSubtle": true,
                    "wrap": true
                  }
                ],
                "width": "stretch"
              }
            ]
          },
          {
            "type": "TextBlock",
            "text": "<at>pullrequests</at> : {{ data.pullrequest.title }}",
            "wrap": true
          },
          {
            "type": "FactSet",
            "facts": [
              {
                "title": "Repository",
                "value": "{{ data.repository.name }}"
              },
              {
                "title": "Branch",
                "value": "{{ data.pullrequest.source.branch.name }}"
              },
              {
                "title": "Status",
                "value": "{{ data.pullrequest.state }}"
              }
            ]
          }
        ],
        "$schema": "http://adaptivecards.io/schemas/adaptive-card.json",
        "version": "1.0",
        "actions": [
          {
            "type": "Action.OpenUrl",
            "title": "Open",
            "url": "{{ data.pullrequest.links.html.href }}"
          }
        ],
        "msteams": {
          "entities": [
            {
              "type": "mention",
              "text": "<at>pullrequests</at>",
              "mentioned": {
                "id": "YOUR TEAMS ID",
                "conversationIdentityType": "channel"
              }
            }
          ]
        }
      }
    }
  ]
}