Add additional ignore_headers audit configuration setting

[stephen-crawford]

Description

This change adds a new setting to the audit.yml configuration allowing users to specify REST headers they wish to be ignored from audit logging.

Issues Resolved

• Resolves Redact custom headers from audit logging  #3875

Testing

Added a couple new test cases to check the setting

Check List

• New functionality includes testing
• New functionality has been documented
• Commits are signed per the DCO using --signoff

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[cwperks]

LGTM! I left one small suggestion around naming the method on the filter.

[DarshitChanpura]

LGTM. Left few nits

[DarshitChanpura]

There is a compilation error:

/home/runner/work/security/security/src/test/java/org/opensearch/security/auditlog/impl/AuditMessageTest.java:79: error: cannot find symbol
        when(auditConfig.getFilter().isHeaderDisabled("test-header")).thenReturn(false);

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Comparison is base (26e62d5) 65.18% compared to head (6d630d1) 65.21%.

Additional details and impacted files

@@            Coverage Diff             @@
##             main    #3885      +/-   ##
==========================================
+ Coverage   65.18%   65.21%   +0.02%     
==========================================
  Files         298      298              
  Lines       21195    21210      +15     
  Branches     3456     3457       +1     
==========================================
+ Hits        13817    13832      +15     
  Misses       5664     5664              
  Partials     1714     1714              

Files	Coverage Δ
.../opensearch/security/OpenSearchSecurityPlugin.java	84.53% <100.00%> (+0.09%)	⬆️
...ensearch/security/auditlog/config/AuditConfig.java	99.22% <100.00%> (+0.05%)	⬆️
...earch/security/auditlog/impl/AbstractAuditLog.java	76.20% <ø> (ø)
...pensearch/security/auditlog/impl/AuditMessage.java	75.00% <100.00%> (+0.24%)	⬆️
...g/opensearch/security/support/ConfigConstants.java	95.23% <ø> (ø)

[peternied]

@scrawfor99 Do you have a link to the documentation update?