Using probot to receive events from other GitHub apps

[roi-orca]

Feature Request

We are working on integrating our product with GitHub enterprise and for that, we want to use the same URL defined in our GitHub app hook_attributes for the GitHub app that will be created in the GitHub enterprise of the customer.

The problem will be upon receiving the event and validating the signature, that uses our GitHub app configuration and not the customer's GitHub app configuration.

I would like to add a pre-hook that will inject Probot with the customer details (base url, app id, private key, webhook secret) for that specific request instead of using the default one created while bootstrapping the server.

[welcome]

Thanks for opening this issue. A contributor should be by to give feedback soon. In the meantime, please check out the contributing guidelines and explore other ways you can get involved.