[Backport 2.x] Username validation for special characters

[opensearch-trigger-bot]

Backport efbc48b from #2277

[codecov-commenter]

Codecov Report

Merging #2317 (efbc48b) into 2.x (b7bf4a2) will increase coverage by 0.03%.
The diff coverage is 77.77%.

❗ Current head efbc48b differs from pull request most recent head 66823a2. Consider uploading reports for the commit 66823a2 to get more accurate results

@@             Coverage Diff              @@
##                2.x    #2317      +/-   ##
============================================
+ Coverage     61.04%   61.08%   +0.03%     
- Complexity     3248     3270      +22     
============================================
  Files           258      260       +2     
  Lines         18125    18369     +244     
  Branches       3231     3251      +20     
============================================
+ Hits          11065    11220     +155     
- Misses         5490     5562      +72     
- Partials       1570     1587      +17     

Impacted Files	Coverage Δ
...ic/auth/http/jwt/AbstractHTTPJwtAuthenticator.java	55.81% <ø> (ø)
...mazon/dlic/auth/http/jwt/HTTPJwtAuthenticator.java	85.71% <ø> (ø)
...ic/auth/http/kerberos/HTTPSpnegoAuthenticator.java	0.00% <0.00%> (ø)
...dlic/auth/http/saml/AuthTokenProcessorHandler.java	47.28% <0.00%> (ø)
...auth/http/saml/SamlFilesystemMetadataResolver.java	0.00% <0.00%> (ø)
...tion/configupdate/TransportConfigUpdateAction.java	100.00% <ø> (ø)
...security/auditlog/sink/ExternalOpenSearchSink.java	59.25% <0.00%> (ø)
...security/configuration/DlsFlsFilterLeafReader.java	61.98% <ø> (ø)
...search/security/configuration/DlsFlsValveImpl.java	59.47% <ø> (ø)
...earch/security/dlic/rest/api/MigrateApiAction.java	4.34% <ø> (+0.18%)	⬆️
... and 76 more

Help us with your feedback. Take ten seconds to tell us how you rate us. Have a feature suggestion? Share it here.