Change OTEL user attribute

[p29876]

• change user attribute to OTEL standard enduser.id that can be picked up by external OTEL dashboards
• make constants for other attributes to ensure consistency

[sonarqubecloud]

Quality Gate passed

Issues
0 New issues
0 Accepted issues

Measures
0 Security Hotspots
0.0% Coverage on New Code
0.0% Duplication on New Code

See analysis details on SonarCloud

[codecov]

Codecov Report

Attention: Patch coverage is 75.00000% with 4 lines in your changes missing coverage. Please review.

Project coverage is 67.91%. Comparing base (2b89f94) to head (ba93fcb).
Report is 1 commits behind head on develop.

Files with missing lines	Patch %	Lines
...gchq/gaffer/rest/controller/GremlinController.java	57.14%	2 Missing and 1 partial ⚠️
...store/operation/handler/OperationChainHandler.java	50.00%	1 Missing ⚠️

Additional details and impacted files

@@              Coverage Diff              @@
##             develop    #3321      +/-   ##
=============================================
- Coverage      67.91%   67.91%   -0.01%     
  Complexity      2596     2596              
=============================================
  Files            952      952              
  Lines          30469    30477       +8     
  Branches        3361     3362       +1     
=============================================
+ Hits           20692    20697       +5     
- Misses          8305     8307       +2     
- Partials        1472     1473       +1     

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