fix: allow null values to be passed in Braze for standard properties

[yashasvibajpai]

Description of the change

Braze allows passing null as a traits value for standard as well as custom attributes in Identify Calls. We are adding support for standard attributes also.

Type of change

• Bug fix (non-breaking change that fixes an issue)
• New feature (non-breaking change that adds functionality)
• Breaking change (fix or feature that would cause existing functionality to not work as expected)

Related issues

Fix #1

Checklists

Development

• Lint rules pass locally
• The code changed/added as part of this pull request has been covered with tests
• All tests related to the changed code pass in development

Code review

• This pull request has a descriptive title and information useful to a reviewer. There may be a screenshot or screencast attached
• "Ready for review" label attached to the PR and reviewers mentioned in a comment
• Changes have been reviewed by at least one other engineer
• Issue from task tracker has a link to this pull request

[codecov]

Codecov Report

Patch coverage: 100.00% and project coverage change: +0.01 🎉

Comparison is base (c4b0a69) 87.87% compared to head (adc27ac) 87.89%.

❗ Current head adc27ac differs from pull request most recent head 962d8c2. Consider uploading reports for the commit 962d8c2 to get more accurate results

Additional details and impacted files

@@             Coverage Diff             @@
##           develop    #2111      +/-   ##
===========================================
+ Coverage    87.87%   87.89%   +0.01%     
===========================================
  Files          509      509              
  Lines        25771    25769       -2     
  Branches      6380     6379       -1     
===========================================
+ Hits         22647    22649       +2     
+ Misses        2789     2787       -2     
+ Partials       335      333       -2     

Impacted Files	Coverage Δ
src/v0/destinations/braze/util.js	97.14% <ø> (-0.06%)	⬇️
src/v0/destinations/braze/transform.js	84.08% <100.00%> (+1.63%)	⬆️

... and 2 files with indirect coverage changes

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[sonarcloud]

Kudos, SonarCloud Quality Gate passed!   

0 Bugs
0 Vulnerabilities
0 Security Hotspots
179 Code Smells

86.8% Coverage
4.3% Duplication