Correctly calculate used space for quota with external storage

[MorrisJobke]

• fixes External storage quota #4348
• Correctly calculate used space for quota with external storage #4357 + fixes of unit tests

I tested this and it works here.

[mention-bot]

@MorrisJobke, thanks for your PR! By analyzing the history of the files in this pull request, we identified @icewind1991, @nickvergessen and @blizzz to be potential reviewers.

[MorrisJobke]

cc @Ardinis

[nickvergessen]

Missing signatures on:

• 46b398e

and the remaining checks are not executed anymore. Maybe we should extract the signature one or move it to the end.

[codecov]

Codecov Report

Merging #4816 into master will increase coverage by 0.01%.
The diff coverage is 100%.

@@             Coverage Diff             @@
##             master   #4816      +/-   ##
===========================================
+ Coverage     54.19%   54.2%   +0.01%     
+ Complexity    22154   22150       -4     
===========================================
  Files          1363    1363              
  Lines         84842   84804      -38     
  Branches       1322    1322              
===========================================
- Hits          45976   45964      -12     
+ Misses        38866   38840      -26

Impacted Files	Coverage Δ	Complexity Δ
lib/private/legacy/helper.php	78.14% <100%> (ø)	116 <0> (+1)	⬆️
apps/comments/lib/EventHandler.php	79.16% <0%> (-8.34%)	7% <0%> (ø)
core/js/js.js	61.21% <0%> (-0.57%)	0% <0%> (ø)
config/config.sample.php	0% <0%> (ø)	0% <0%> (ø)	⬇️
core/Command/Upgrade.php	0% <0%> (ø)	28% <0%> (ø)	⬇️
core/ajax/update.php	0% <0%> (ø)	11% <0%> (ø)	⬇️
lib/private/Updater.php	5.9% <0%> (+0.12%)	73% <0%> (ø)	⬇️
core/Controller/LoginController.php	78.12% <0%> (+1.2%)	37% <0%> (-1%)	⬇️
lib/private/App/AppStore/Fetcher/AppFetcher.php	77.77% <0%> (+2.77%)	15% <0%> (ø)	⬇️
core/Controller/LostController.php	83.58% <0%> (+3.16%)	26% <0%> (-3%)	⬇️
... and 2 more

[MorrisJobke]

Fixed the signature.

[MorrisJobke]

They run fine now -> merge