Prevent memory leak

[YoavGro]

Change the TokenGetter to a weak reference to prevent a memory leak in the client.

The client holds the CentrifugeClientConfig which has a strong reference to a CentrifugeConnectionTokenGetter
The problem can happen once the CentrifugeConnectionTokenGetter implementation is the one that is holding a strong reference to the Client.

This creates a circular strong reference Between the App -> Client -> Config -> TokenGetter -> App

[FZambia]

@YoavGro hello, thanks a lot for PR!

What do you think - it seems we better add the same to Subscription tokenGetter?

centrifuge-swift/Sources/SwiftCentrifuge/Subscription.swift

Line 36 in 783e7a2

public var tokenGetter: CentrifugeSubscriptionTokenGetter?

[YoavGro]

Yep, good idea.
Done

[FZambia]

Thanks! I'll try to make a new release till the end of this week