Hi!
Justin here with the support engineering team 
If you use an Application Webhook, we include an auth object on the payload, so you could determine the customer from there (via a DB lookup on your side) then forward on to the destination.
If you use Application Webhooks, you can't configure any attributes on a per-installation basis. The link posted is only when the Application developers configure their webhook, not when any customers install an application webhook.
During the setup phase you should receive an auth object with the Front company ID. Provided you record this, you could then map a Front company ID to your own user ID. Then every payload received will continue to contain a company ID and you could can map based that.
A few additional notes:
- Published Webhooks work hand-in-hand with an OAuth Client: If an application defines a webhook, the application developer will need to request a token (via OAuth) to enable the webhook.
- All webhook requests contain the
authorization.id property with the ID of the customer (company) that emitted the event. - A token can request its identity (
GET /me) to get the ID of the customer
If there are any other questions, please do not hesitate to reach out!