Use Firestore's auto-generated id instead of a random UUID

[thatfiredev]

I've noticed how this app is using UUID.randomUUID().toString() to generate a document ID and save it on Firestore:

make-it-so-android/app/src/main/java/com/example/makeitso/model/service/impl/StorageServiceImpl.kt

Lines 69 to 73 in 40e46da

	Firebase.firestore
	.collection(TASK_COLLECTION)
	.document(task.id)
	.set(task)
	.addOnCompleteListener { onResult(it.exception) }

It would be nice to demonstrate Firestore's auto-generated ids instead:

 Firebase.firestore 
     .collection(TASK_COLLECTION) 
     .add(task) 
     .addOnCompleteListener { onResult(it.exception) } 

And when reading the tasks, we'd manually set the id:

value?.documentChanges?.forEach {
    val wasDocumentDeleted = it.type == REMOVED
    val task = it.document.toObject<Task>().apply { task.id = it.document.id  }
    onDocumentEvent(wasDocumentDeleted, task)
}

[marinacoelho]

Fixed by: #9