Implement fork method in the Receiver

[ela-kotulska-frequenz]

This is useful for scenarios where multiple consumers need to process the same stream of messages.

[ela-kotulska-frequenz]

But I am not sure this is correct way, because fork for FileWatcher or Timer looks strange. And I don't see any use case for them.
If we agree to go with it, then I will add tests and improve the code.

[shsms]

I didn't realize you were picking this already, I think the proposal needs some changes (sorry, I should have written something earlier).

fork doesn't tell if it should be a broadcast or anycast style behaviour, and users might need different things. I would prefer using experimental.Pipe for this purpose instead because then, we don't just inherit the behaviour of anycast/broadcast receivers, and don't create additional timers, filewatchers etc, but instead just broadcast their results.

[llucax]

Same here, I just wrote it as a proposal, without thinking too much about it, just so we don't forget to discuss it but I didn't think you were going to take it so fast, I guess it probably needs a bit more discussion and thought. Maybe we can discuss in the next SDK meeting.

[llucax]

BTW, from my side we didn't have to close this, only that it needed a bit more discussion. At least I think it could still be a valid approach.

[llucax]

fork doesn't tell if it should be a broadcast or anycast style behaviour, and users might need different things. I would prefer using experimental.Pipe for this purpose instead because then, we don't just inherit the behaviour of anycast/broadcast receivers, and don't create additional timers, filewatchers etc, but instead just broadcast their results.

BTW, the original proposal (I didn't check the code in the PR yet) suggested it is basically a proxy for underlaying_source.new_receiver() so if you fork a broadcast receiver, you get another broadcast receiver, if you fork a anycast receiver, you get a new anycast receiver. So I don't think this is ambiguous, at least as long as you know what type of receiver you are forking.