Make it possible to consume notifications in all app states and present them appropriately

[cpetrov]

Problem description

Current state:

• data only messages don't show notification banners on iOS.

e.g.

    {
      to: ...,
      data: {
        title: 'title',
        body: 'body',
        payload: {}
      }
    }    

• notification/data messages show banners on iOS. e.g.

  {
    to: ...,
    data: {
      title: 'title',
      body: 'body',
      payload: {}
    },
    notification: {
      title: 'title',
      body: 'body'
    }
  }    

  When a data only message is received:

app killed (cold start through tap on notification)	app in bg	app in fg
"message" event fired	cannot launch, since no banner is shown	✔	✔

When a notification/data mixed message is received:

app killed (cold start through tap on notification)	app in bg (either opened through tap on banner or app icon)	app in fg
"message" event fired	✖	✖	✔
launchData set	✖	-	-

Expected behavior

There should be a way to show a notification banner in the system UI when:

• the app is killed
• the app is in the background

There should be a way to consume a notification in the app when:

• the app is killed and is being launched
• the app is in the background and is being launched
• the app is in the foreground

... ideally only using the "message" event and the launchData property if this is possible.

[cpetrov]

This may be helpful: https://firebase.google.com/docs/cloud-messaging/ios/receive

[patrykmol]

I have updated plugin. Hook is now fixed and launchData is now properly propagated. All of the mixed scenarios work in the example app.

Do note that when app is in background or when doing cold start data from regular notification will always land in launchData. message event is fired when app is in foreground.