This feature request has been accepted by the feature team and is actively being worked upon!
Planner is being worked upon, the topic is found at:
OneNote has been added and can be found in the store link within Teams.
Other items are still being added and third party bots and apps are being created as well.
An error occurred while saving the commentLuigi Vecchione commented
This would be a great feature! Discovering it wasn't already available has left me soo disappointed, i'll follow the post waiting for any interesting update.