Force backup before applying an update

Summary

Following 0.12 release in beginning of October which caused data loss for few users, we are thinking about some ways to protect user data in case of a failure during the update process.

The idea would be, for users who have an ecloud account (and enough space on it), to run a backup before applying the update. It would also be to make sure no file synchronization is in progress.

Description

Who will use the new feature?

All /e/ users with an ecloud account

What is the target of the new feature for this user?

Avoid data loss in case of a failure in update process

Why this user would like to use this feature?

Trust in /e/ as it protect more their data

Examples

## Reflection

1. The user receives a notification for the update
2. The user starts the download
3. The user starts the install
4. Before installing the update, the Updater ask Seedvault to run a backup. The updater starts the install process only once the update is done an uploaded to ecloud
5. The Updater install the update
6. If something goes wrong, the user can reinstall his device an recover his data

Mockups

Diagrams

Validation