Add Method to Clear Inbox

[nixpulvis]

I think I need a method to clear an inbox. My use case is in implementing a button click which locks the application and clears user data. I have some inboxes which are used to load user data. What I don't want to happen is that I lock the app, then an inbox is read and the user is still loaded.

I can work around this by putting the read calls behind a logged in flag which locking the app sets, but I then worry about duplicate messages when the user logs in again.

Open to other ideas, and thanks for the simple and great crate.

[nixpulvis]

I guess I can justs set the inbox to a new inbox... I haven't tested this though.

[lucasmerlin]

Yeah I think self.inbox = UiInbox::new() should work 👍🏻 I'm also happy to accept a PR that implements a reset method that basically does this