Feat add tests

[Giacomo92]

• test all entities
• test all validation rules
• create all stub responses

[codecov]

Codecov Report

Merging #41 (0d7cef5) into develop (b4688f3) will increase coverage by 16.94%.
The diff coverage is n/a.

@@              Coverage Diff               @@
##             develop      #41       +/-   ##
==============================================
+ Coverage       3.38%   20.33%   +16.94%     
  Complexity       105      105               
==============================================
  Files             21       21               
  Lines            354      354               
==============================================
+ Hits              12       72       +60     
+ Misses           342      282       -60     

Impacted Files	Coverage Δ
src/Requests/Common.php	46.15% <0.00%> (+46.15%)	⬆️
src/FattureInCloud.php	50.00% <0.00%> (+50.00%)	⬆️
src/Auth.php	56.25% <0.00%> (+56.25%)	⬆️
src/Entities/Account.php	60.52% <0.00%> (+60.52%)	⬆️
src/Requests/Account.php	100.00% <0.00%> (+100.00%)	⬆️

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