Block GET request on secondary/relationship endpoint when AllowView is off

[bkoelman]

Block GET request on secondary/relationship endpoint when the relationship doesn't contain the AllowView capability

Fixes #1991.

QUALITY CHECKLIST

• Changes implemented in code
• Complies with our contributing guidelines
• Adapted tests
• Documentation updated

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 92.22%. Comparing base (08573c6) to head (f40ed9b).
⚠️ Report is 1 commits behind head on master.

Additional details and impacted files

@@           Coverage Diff           @@
##           master    #1992   +/-   ##
=======================================
  Coverage   92.21%   92.22%           
=======================================
  Files         437      438    +1     
  Lines       14946    14962   +16     
  Branches     2476     2480    +4     
=======================================
+ Hits        13782    13798   +16     
  Misses        714      714           
  Partials      450      450           

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