what is the idiomatic way to implement a resources pool with Flows? let's say it's a list of numbers 1..10 that can grow and shrink resources.borrow { resource -> ... } then once a resource is done being borrowed, it is returned to the pool, if no resources are available, it waits until another borrow is completed a secondary thread can add resources or remove resources from the pool if they are no longer valid I think this is possible with Channels, but would like to use a cold flow.