<<Resurfacing the information from comments to here for broader community usage>>
Currently using Azure Active Directory you can authenticate your webhook connection as per steps documented here.
Using the webhook action requires that the target webhook endpoint either doesn't require details of the alert to function successfully or it's capable of parsing the alert context information that's provided as part of the POST operation. If the webhook endpoint can't handle the alert context information on its own, you can use a solution like a Logic App action for a custom manipulation of the alert context information to match the webhook's expected data format.
Hope the information helps, please revert back if you have any additional queries.