New endpoint — Create an asset from an alert

Added POST /v2/alert/assets to create an asset directly from an alert. Provide exactly one of id or entity to identify the alert, and asset_type in the body. Doppel reads the asset value and the brand from the alert, so you do not send them.

The alert must be one your organization can read. A request that names an alert your organization cannot read returns 404.

This endpoint is available on V2 only.