Fix/v5 i18n

[cyp3rius]

Ticket

#461
#459

Summary

What does this PR do/solve?

Resolves multiple issues related with Strapi i18n and finally enables full & native compatibility with this feature.

Test Plan

N/A

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 89.04%. Comparing base (154ba72) to head (8efc9ab).
Report is 1 commits behind head on v5.

Additional details and impacted files

@@           Coverage Diff           @@
##               v5     #463   +/-   ##
=======================================
  Coverage   89.04%   89.04%           
=======================================
  Files          19       19           
  Lines         283      283           
  Branches       45       45           
=======================================
  Hits          252      252           
  Misses         30       30           
  Partials        1        1           

Flag	Coverage Δ
unittest	89.04% <ø> (ø)

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