Requested by Chop Chop via Telegram.

Provide a 'second layer' of unlocks. The base layer would be the standard Sablier streaming logic. The added-on layer would be a switch that is required for unlocking the tokens even after they have passed the base layer cliff.

In other words: a pre-programmed stream with a secondary trigger controlled by an admin account that can unlock/execute the so-far streamed base layer. After that trigger, every stream in the future is by default locked again until triggered again.