In all of our current uses of os.umask or filesystem.umask, we always temporarily set it to a different value and then restore it using a try/finally block. I expect this pattern to continue.

Because of that, why don't we create a simple function in certbot.util that can be used as a context manager to set umask to a value and restore it to its previous value when exiting the with blo

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Issue Description

When using the RateLimiter Middleware with a rate between 0 and 1 all events will be rejected instead of applying the specified rate. E.g.: e.Use(middleware.RateLimiter(middleware.NewRateLimiterMemoryStore(0.5)))

I am not saying that it is a common use case to have

It could be useful to allow for controller's sync period to be configurable.

Background:
See Kubernetes sample controller diagram for reference. cert-manager's controller consists of a number of control loops that sync various cert-manager's and Ku