HandlerWithRecovery is http handler middleware that gracefully handles panics by calling a deferred recover for all wrapped handlers.

PanicInterceptor wraps the panic recovery handler grpcRecoveryHandler for use as a UnaryServerInterceptor.

PanicStreamInterceptor wraps the panic recovery handler grpcRecoveryHandler for use as a StreamServerInterceptor.

ContextKeyCluster is the key used to put and retrieve `*model.RequestCluster` into context.