Add utils::sanitize-entity tests

[Convly]

Add tests for sanitize-entity.
Rise coverage to 100% and handle edge cases;

[codecov]

Codecov Report

Merging #7497 into master will increase coverage by 0.16%.
The diff coverage is 75.00%.

@@            Coverage Diff             @@
##           master    #7497      +/-   ##
==========================================
+ Coverage   26.21%   26.38%   +0.16%     
==========================================
  Files        1131     1131              
  Lines       15440    15442       +2     
  Branches     2438     2439       +1     
==========================================
+ Hits         4048     4074      +26     
+ Misses       9576     9559      -17     
+ Partials     1816     1809       -7     

Flag	Coverage Δ
#front	18.25% <ø> (ø)
#unit	53.85% <75.00%> (+0.70%)	⬆️

Flags with carried forward coverage won't be shown. Click here to find out more.

Impacted Files	Coverage Δ
packages/strapi/lib/core-api/controller.js	23.07% <0.00%> (ø)
packages/strapi-utils/lib/sanitize-entity.js	100.00% <100.00%> (+38.70%)	⬆️

---

Continue to review full report at Codecov.

Legend - Click here to learn more
Δ = absolute <relative> (impact), ø = not affected, ? = missing data
Powered by Codecov. Last update b39709a...6dff656. Read the comment docs.

[petersg83]

Looks good to me, just a few questions

[petersg83]

LGTM :)