Github webhook provider / store?

[jhosteny]

It would be nice to be able to have sidecred add a secret and config setting for GH webhooks, so that PR builds could be triggered without a resource check.

It's a bit of a strange case, since you would potentially have sidecred generate a random secret, then store it on the webhook setting for the repo along with the config settings (e.g., URL to write to). In that sense, it is actually a store.