[Story] Add application settings screen for notifications

[giomfo]

As a user, I want to be able to enable/disable my registration to the push notifications on my current device

Design: iOS, Android

Scope

Android

Beta Give feedback

1. Add a sub-screen "Notifications" in the existing application Settings vector-im/element-x-android#510
   A-Notifications T-Task +2
   
2. Add in Notifications settings the option to enable/disable notification on this device vector-im/element-x-android#531
   A-Notifications T-User Story +2
   
3. Display in Notifications settings the default mode for the group and the direct chats vector-im/element-x-android#532
   A-Notifications T-Task +2
   
4. Add in Notifications settings a toggle for room mentions and another one for VoIP calls vector-im/element-x-android#533
   A-Notifications T-Task +2
   
5. Edit the default notification settings for the Group chats vector-im/element-x-android#534
   A-Notifications T-Task X-Needs-Signoff +3
6. List the chats with a custom notification setting vector-im/element-x-android#536
   A-Notifications T-Task +2
7. Add a group chat to the list by defining a new custom notification setting vector-im/element-x-android#537
   A-Notifications +1
8. Edit the default notification settings for the Direct chats vector-im/element-x-android#538
   A-Notifications A-Performance T-Task +3
9. Edit the custom settings from the Global Notification settings vector-im/element-x-android#539
   A-Notifications T-Task +2
10. Add a direct chat to the list by defining a new custom notification setting vector-im/element-x-android#540
    A-Notifications +1

iOS

Beta Give feedback

1. Add a sub-screen "Notifications" in the existing application Settings vector-im/element-x-ios#1022
   A-Notifications +1
2. Add in Notification settings the option to enable/disable notifications on this device vector-im/element-x-ios#1023
   A-Notifications T-Enhancement +2
3. Display in Notifications settings the default mode for the group and the direct chats vector-im/element-x-ios#1024
   A-Notifications T-Enhancement X-Needs-Design +3
   
4. Add in Notifications settings a toggle for room mentions and another one for VoIP calls vector-im/element-x-ios#1025
   A-Notifications T-Enhancement +2
5. Edit the default notification settings for the Group chats vector-im/element-x-ios#1026
   A-Notifications T-Enhancement +2
6. List the chats with a custom notification setting vector-im/element-x-ios#1027
   A-Notifications T-Enhancement +2
7. Add a group chat to the list by defining a new custom notification setting vector-im/element-x-ios#1028
   A-Notifications T-Enhancement +2
8. Edit the default notification settings for the Direct chats vector-im/element-x-ios#1029
   A-Notifications T-Enhancement +2
9. Edit the custom settings from the Global Notification settings vector-im/element-x-ios#1030
   A-Notifications T-Enhancement +2
10. Add a direct chat to the list by defining a new custom notification setting vector-im/element-x-ios#1031
    A-Notifications T-Enhancement +2

Tasklist

Beta Give feedback

1. QA signoff on completion
2. Design signoff on completion
3. Product signoff on completion

Stretch goals

None at this time

Out of scope

[giomfo]

@langleyd here is the update of this Story:

• first @amshakal and I decided to remove from the current scope the possibility to add a custom room notification setting from the global settings. This is doable from the room settings.

• iOS: all the work has been done (thx @nimau). It is available in the nightly release behind the Developer Option "Show notification settings" (disabled by default). All my tests were ok. This platform is ready for the QA/Design signoff.

• Android: This PR is related to the 4 first Android issues (assigned to @yostyle). Only the UI has been implemented for this screen. You will need to plug this UI with the interface set up by @nimau at the Rust level.

cc @VolkerJunginger