Upgrade to Twig 3.8

[osma]

Reasons for creating this PR

Getting rid of EOL'd Twig 2.

Link to relevant issue(s), if any

• Closes Upgrade to Twig 3 for Skosmos 3 #1585

Description of the changes in this PR

• bump Twig dependency to 3.8.*
• adjust to API changes (in PHP code) between Twig 2 and 3

No Twig templates were harmed when performing this upgrade. (In other words, the templates themselves are unchanged.)

Known problems or uncertainties in this PR

n/a

Checklist

• phpUnit tests pass locally with my changes
• I have added tests that show that the new code works, or tests are not relevant for this PR (e.g. only HTML/CSS changes)
• The PR doesn't reduce accessibility of the front-end code (e.g. tab focus, scaling to different resolutions, use of .sr-only class, color contrast)
• The PR doesn't introduce unintended code changes (e.g. empty lines or useless reindentation)

[sonarqubecloud]

Quality Gate passed

Kudos, no new issues were introduced!

0 New issues
0 Security Hotspots
No data about Coverage
0.0% Duplication on New Code

See analysis details on SonarCloud

[codecov]

Codecov Report

Attention: 8 lines in your changes are missing coverage. Please review.

Comparison is base (d0aa524) 70.54% compared to head (5b4b419) 70.54%.
Report is 8 commits behind head on main.

Files	Patch %	Lines
src/controller/WebController.php	38.46%	8 Missing ⚠️

Additional details and impacted files

@@            Coverage Diff            @@
##               main    #1588   +/-   ##
=========================================
  Coverage     70.54%   70.54%           
  Complexity     1644     1644           
=========================================
  Files            32       32           
  Lines          4315     4315           
=========================================
  Hits           3044     3044           
  Misses         1271     1271           

☔ View full report in Codecov by Sentry.
📢 Have feedback on the report? Share it here.