can someone explain a bit how the @before hooks works in detail,
i mainly have problems understanding why ensureAuth in belows example refers to
"SampleService." as an instance: https://github.com/rejectedsoftware/vibe.d/blob/a1efc05c09135ca8aca21ccec72790ddfaca67c9/examples/web/source/app.d#L114 so how does PrivateAccessProxy work: https://github.com/rejectedsoftware/vibe.d/blob/master/source/vibe/internal/meta/funcattr.d#L225
