[Backport 2.x] Fixes authtoken endpoint

[opensearch-trigger-bot]

Backport 9e62096 from #4628.

[codecov]

Codecov Report

Attention: Patch coverage is 30.00000% with 7 lines in your changes missing coverage. Please review.

Project coverage is 65.38%. Comparing base (1632726) to head (78aa5fd).

Files	Patch %	Lines
...java/org/opensearch/security/user/UserService.java	16.66%	5 Missing ⚠️
.../security/dlic/rest/api/CertificatesApiAction.java	0.00%	1 Missing ⚠️
...security/dlic/rest/api/InternalUsersApiAction.java	66.66%	0 Missing and 1 partial ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##              2.x    #4631      +/-   ##
==========================================
- Coverage   65.39%   65.38%   -0.01%     
==========================================
  Files         316      316              
  Lines       22140    22140              
  Branches     3578     3578              
==========================================
- Hits        14478    14476       -2     
- Misses       5869     5872       +3     
+ Partials     1793     1792       -1     

Files	Coverage Δ
.../security/dlic/rest/api/CertificatesApiAction.java	35.13% <0.00%> (-0.98%)	⬇️
...security/dlic/rest/api/InternalUsersApiAction.java	76.85% <66.66%> (ø)
...java/org/opensearch/security/user/UserService.java	44.92% <16.66%> (-0.40%)	⬇️

... and 2 files with indirect coverage changes