Implement backup strategy

[christophehenry]

This prevents loosing settings and flow upon restoration. I don't know how it will handle cached images, though. Would the app refetch them?

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 18.34%. Comparing base (44d00e3) to head (ef96662).
Report is 12 commits behind head on develop.

Additional details and impacted files

@@              Coverage Diff              @@
##             develop     #310      +/-   ##
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+ Coverage      17.73%   18.34%   +0.61%     
  Complexity       460      460              
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  Files            190      190              
  Lines          10327    10208     -119     
  Branches        1611     1466     -145     
=============================================
+ Hits            1831     1873      +42     
+ Misses          8398     8230     -168     
- Partials          98      105       +7     

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[Shinokuni]

After reading the docs about Android native backup, I would have a few things to say.

First, the maximum amount of backup data supported by Google Drive, which is one of the provided backup strategies doesn't exceed 25MB. This is not that much, on my personal device I got over 70MB of data (excluding cache and app code). Anyone who would be using Readrops since at least more than a year or has a large amount of feeds wouldn't have its data backed up on Google Drive.

About preferences, the docs say that shared preferences are found in their directory, meaning shared_prefs, but Readrops uses DataStore which stores preferences in files/datastore. But the docs also specify that the whole app internal storage is backed up by default, so there is no need to specify preferences in the backup strategy.

Overall, I don't think that Android native backup is reliable enough, so I don't know what to think about this. It seems better than nothing, but a proper backup feature is needed and planned (although I don't know when it comes).

[christophehenry]

Ok. Not a big deal. Re-init the app is quite straightforward.