[Prep] EC in EX: Build the foundations

[manuroe]

Description

Whatever UX decisions we need to be able to embed Element Call in a web view and connect it to the Widget API in the Rust SDK.
The Widget API implementation is a WIP but it is possible to work in parallel as suggested here.
For future purpose, the implementation of the webview should be considered for a generic widget, not only for call. We want more widgets in the future.

Size estimate

M

Dependencies

• https://github.com/vector-im/voip-internal/issues/193

Acceptance criteria

• Element Call is opened in a fullscreen web view via an URL
• Element Call sends JSON events to the Widget API
• Element Call receives JSON events from the Widget API
• Permissions are asked as expected
• Element Call continues to work when the app is in bg or device locked
• Current audio playing is stopped when entering the call and resumed when leaving the call
• App can request Element Call to stop the call

Out of scope

• Bundling the web app with the app package. We use a URL for now

Subtasks

Android

Beta Give feedback

1. [Element Call] Microphone and camera permissions vector-im/element-x-android#1540
   A-VOIP T-Task +2
   
2. [Element Call] Allow the call to keep running in the background vector-im/element-x-android#1541
   A-VOIP T-Task +2
   
3. [Element Call] Allow the call to keep running while the device is locked vector-im/element-x-android#1542
   A-VOIP T-Task +2
   
4. [Element Call] Display system UI that a call is ongoing vector-im/element-x-android#1543
   A-VOIP T-Task +2
   
5. [Element Call] Pause (and resume) other system audio while call is running vector-im/element-x-android#1544
   A-VOIP T-Task +2
   
6. [Element Call] Create bridge between WebApp and Rust vector-im/element-x-android#1545
   A-VOIP T-Task +2
   

iOS

Beta Give feedback

1. [Element Call] Microphone and camera permissions vector-im/element-x-ios#1442
   A-VOIP T-Task +2
   
2. [Element Call] Allow the call to keep running in the background vector-im/element-x-ios#1443
   A-VOIP T-Task +2
   
3. [Element Call] Allow the call to keep running while the device is locked vector-im/element-x-ios#1444
   A-VOIP T-Task +2
   
4. [Element Call] Display system UI that a call is ongoing vector-im/element-x-ios#1445
   A-VOIP T-Task +2
   
5. [Element Call] Pause (and resume) other system audio while call is running vector-im/element-x-ios#1446
   A-VOIP T-Task +2
   
6. [Element Call] Create bridge between WebApp and Rust vector-im/element-x-ios#1447
   A-VOIP T-Task +2