Fixed fields validation bypass

[MDeLuise]

Brief description of the PR
While editing an existing user account or creating a new children account, it is possible to bypass the length and composition policies enforced by the application frontend to, respectively, the password and account name fields.
This PR fixes this problems adding the validation of the fields even in the service backend.

[codecov]

Codecov Report

Merging #3527 (cfcc196) into develop (80972c3) will decrease coverage by 5.70%.
The diff coverage is 33.33%.

❗ Current head cfcc196 differs from pull request most recent head 7957123. Consider uploading reports for the commit 7957123 to get more accurate results

@@              Coverage Diff              @@
##             develop    #3527      +/-   ##
=============================================
- Coverage      50.25%   44.55%   -5.71%     
+ Complexity       259      184      -75     
=============================================
  Files           1647     1647              
  Lines          31666    31675       +9     
  Branches        2621     2624       +3     
=============================================
- Hits           15913    14112    -1801     
- Misses         14823    16738    +1915     
+ Partials         930      825     -105     

Impacted Files	Coverage Δ
...cation/credential/shiro/CredentialServiceImpl.java	30.98% <28.57%> (-5.43%)	⬇️
...a/service/account/internal/AccountServiceImpl.java	37.85% <50.00%> (-39.68%)	⬇️
...pse/kapua/kura/simulator/GatewayConfiguration.java	0.00% <0.00%> (-100.00%)	⬇️
...a/kura/simulator/birth/BirthCertificateModule.java	0.00% <0.00%> (-100.00%)	⬇️
.../kapua/service/tag/internal/TagListResultImpl.java	0.00% <0.00%> (-100.00%)	⬇️
...rvice/endpoint/internal/EndpointInfoQueryImpl.java	0.00% <0.00%> (-100.00%)	⬇️
.../endpoint/internal/EndpointInfoListResultImpl.java	0.00% <0.00%> (-100.00%)	⬇️
...nnection/internal/DeviceConnectionCreatorImpl.java	0.00% <0.00%> (-100.00%)	⬇️
...ent/packages/message/internal/PackageResource.java	0.00% <0.00%> (-100.00%)	⬇️
...kages/model/internal/DevicePackageOptionsImpl.java	0.00% <0.00%> (-100.00%)	⬇️
... and 116 more