don't perform HTML escaping for server constants to avoid breaking alphabetical index for diacritics

[osma]

Reasons for creating this PR

Alphabetical index was broken for diacritics like Ä, Ä, Ö. This happened because of too strict/eager input sanitizing. This PR fixes the problem (on the master branch, but not skosmos-3 which may be affected too) by reducing the input sanitizing, just performing escaping of quotes. (I'm not sure that's 100% correct either)

Link to relevant issue(s), if any

• Closes Alphabetic tab doesn't work with certain diacritic letters #1574

Description of the changes in this PR

• switch input filtering of server constants from FILTER_SANITIZE_FULL_SPECIAL_CHARS to FILTER_SANITIZE_ADD_SLASHES

Known problems or uncertainties in this PR

• See if the same problem applies for the skosmos-3 branch and fix it there as well

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)

[sonarcloud]

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

All modified and coverable lines are covered by tests ✅

Comparison is base (a1cd362) 70.33% compared to head (9d8511f) 70.33%.

Additional details and impacted files

@@            Coverage Diff            @@
##             master    #1575   +/-   ##
=========================================
  Coverage     70.33%   70.33%           
  Complexity     1669     1669           
=========================================
  Files            32       32           
  Lines          4305     4305           
=========================================
  Hits           3028     3028           
  Misses         1277     1277           

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