avoid calling messageUIDelegate.loaded repeatedly

[andresilveirah]

If the rendering app dispatches the event sp.showMessage multiple times and the consentUI is being presented, clients' app can crash if their code is not guarding against re-presenting the consent ViewController.

Almost entirely inspired on #649

[sampaioroberto]

@andresilveirah Thanks again for merging and crediting #649! 😊

One small concern with the guard: isBeingPresented and view.window only change after the host app calls present(), which happens inside the DispatchQueue.main.async in onSPUIReady. A second event arriving before that block runs would still pass the check and call loaded() twice.

There's also a minor issue in the test: loadMessage() instantiates GenericWebMessageViewController, not MockedGenericWebMessageViewController, so the mockIsBeingPresented override is never active in the duplicated-event scenario. The test passes because toEventually catches the count between the two deliveries rather than the guard actually blocking the second call.

Happy to be wrong if I'm missing something though!

[andresilveirah]

Hey @sampaioroberto you are absolutely right about both, the test and the racing condition when calling loaded(). In the end, I think it'll be easier to deal with it with the flag as you first suggested.

[sampaioroberto]

Hey @andresilveirah Glad it helped! Are you planning to open a new PR with the flag approach, or would you like me to reopen #649?