`.AddGitHubWebHooks();` custom secret value

[Martin Alex Philip Dawson]

.AddGitHubWebHooks(); seems to internally use appsettings.json.

It would be nice to get the value directly myself and pass it in as a parameter because I don't want to use appsettings.json.

Thanks!

[ASP.NET Hello Bot]

This issue was moved to aspnet/AspLabs#36