Context:

We want to enable users to select one webhook per alert to send a notification to when the alert is triggered. This requires an additional dropdown in the alert creation modal.
For more context, see parent ticket

AT:

• There is a dropdown in the alerts creation/update modal with a list of all configured webhooks (if there are any)
• You cannot save an alert that has neither email nor webhook selected
• You can save an alert that has at least one of the two (webhook/email)