Decide what to do with one envelope from one window. With hold: false
a defer is reported but the envelope is not queued, for traffic the
caller refuses instead of holding.
Optionaloptions: AdmitOptionsReturn queued envelopes that may now be dispatched, up to the drain batch size.
Drop all state for a window; call on revocation.
True once a window has been quarantined. Quarantine lasts until release.
Lift quarantine and clear counters for a window; used when the user intervenes.
Ingress guard: flood control in front of the kehto bridge.