Goal

Session and pty decoupled.
Some plugins need more control about Session instances in main process. It would be required, for example, if a plugin want to launch the pty in another host (like #2978) or intercept pty stream to duplicate/record/stream/log it.
Interception can already be done with a middleware in renderer process, but having a Session without a pty can't.

Proposal

I would suggest to add a new API entry: decorateSessionClass(Session). A plugin can expose this function that would return a new class that inherit from the (kind of) Session class received in parameter.

If multiple plugins declare this hook, we would finally get a class that have been multiple times inherited. It can lead to some conflicts but this is already the case for other decorate functions.