Keep CI up-to-date

[swissspidy]

• Install svn on CI to keep tests setup working
• Fix newly reported PHPStan errors

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 72.24%. Comparing base (4989685) to head (bc8dc7a).
⚠️ Report is 1 commits behind head on master.

Additional details and impacted files

@@            Coverage Diff             @@
##             master     #278    +/-   ##
==========================================
  Coverage     72.24%   72.24%            
==========================================
  Files            28       28            
  Lines          1250     1250            
==========================================
  Hits            903      903            
  Misses          347      347            

Flag	Coverage Δ
feature	12.48% <0.00%> (ø)
php	65.03% <100.00%> (ø)

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