Retrieve a single webhook.
{
"created_at": "2016-11-21T12:23:28.000Z",
"enabled": true,
"form_id": "abc123",
"id": "yRtagDm8AT",
"tag": "phoenix",
"updated_at": "2016-11-21T12:23:28.000Z",
"url": "https://test.com",
"verify_ssl": true
}