fix: attributeValue validator should ignore empty string

[vietnguyen]

https://dhis2.atlassian.net/browse/DHIS2-15860

Summary

• Currently metadata attribute values are validated by MandatoryAttributesCheck even when they are an empty string.
• AttributeValidator should ignore empty string. We already have MandatoryAttributesCheck to validate mandatory attributes.
• If user post an empty string for an attribute value which is not mandatory then the existing value will be deleted.

Test

• Add a new Attribute type Email, assign it to User.
• Create or update a User, leave the email attribute blank.
• Expected: create or update User successfully. If updating then existing attribute value is deleted.

[sonarqubecloud]

Kudos, SonarCloud Quality Gate passed!   

0 Bugs
0 Vulnerabilities
0 Security Hotspots
0 Code Smells

0.0% Coverage
0.0% Duplication

[codecov]

Codecov Report

Merging #15262 (26206be) into master (74e4429) will increase coverage by 5.84%.
Report is 3 commits behind head on master.
The diff coverage is 100.00%.

@@             Coverage Diff              @@
##             master   #15262      +/-   ##
============================================
+ Coverage     59.98%   65.83%   +5.84%     
- Complexity    28205    30926    +2721     
============================================
  Files          3483     3483              
  Lines        129117   129141      +24     
  Branches      15044    15046       +2     
============================================
+ Hits          77457    85016    +7559     
+ Misses        45108    37076    -8032     
- Partials       6552     7049     +497     

Flag	Coverage Δ
integration	49.72% <0.00%> (+<0.01%)	⬆️
integration-h2	32.06% <0.00%> (?)
unit	30.15% <100.00%> (+<0.01%)	⬆️

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

Files	Coverage Δ
...alidation/attribute/DefaultAttributeValidator.java	100.00% <100.00%> (ø)

... and 513 files with indirect coverage changes

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