Add a webhook topic for function runs

[mironov]

It can be helpful to:

• Monitor and fix any errors that occur during runs.
• Debug reported issues such as Cart Transform not expanding a bundle.
• Track usage and provide customers with reports on their bundle sales.

It can be authorized by a new scope or, e.g., by existing read_orders.

[thosakwe]

This would be a major improvement for providing merchants with analytics.

Currently, if you want to count the number of orders a discount function has processed, there's not a clear solution.

[sebastianpisula]

+1