Auto-convert V6 configuration instances into V7 configuration instances (for OpenSearch 2.x only)

[nibix]

Description

This is secondary to #4546. Please review #4546 first.

This relates to the proposal "Behind the scenes conversion from V6 to V7" from #4493.
This converts the V6 config instances to V7 config instances "behind the scenes". This allows to save a lot of duplicate implementation regarding to privilege evaluation and possibly also further logic.

As an additional benefit, this makes it possible to use SecurityDynamicConfiguration<> instances in a generically type-safe manner. So far, one usually needs to use SecurityDynamicConfiguration<?> instances and do unsafe casts.

This only touches the runtime representation of the configuration. If there's a V6 configuration in the configuration index, it remains untouched. The possibility to update configuration in V6 format will remain.

This is only for OpenSearch 2.x. For the OpenSearch main branch, #4546 removes V6 config support alltogether.

Behind the scenes conversion

Some more detail on what is changed by this PR:

The configuration architecture consists of these levels:

1. JSON documents in the configuration index
2. ConfigurationRepository which manages SecurityDynamicConfiguration<> instances which contain as entry instances of org.opensearch.security.securityconf.impl.v6.RoleV6, org.opensearch.security.securityconf.impl.v6.RoleMappingsV6, org.opensearch.security.securityconf.impl.v7.RoleV7, org.opensearch.security.securityconf.impl.v7.RoleMappingsV7, etc.
3. DynamicConfigFactory which consumes SecurityDynamicConfiguration<> instances and creates ConfigModel and DynamicConfigModel instances. If it finds V6 classes in SecurityDynamicConfiguration<>, it creates ConfigModelV6 instances, if it finds V7 classes, it creates ConfigModelV7 instances.
4. The ConfigModelV6 and ConfigModelV7 classes contain business logic which evaluates roles and permissions.
5. This is used by PrivilegesEvaluator.

This PR changes the architecture at level 2:

1. The JSON documents in the index do not change
2. ConfigurationRepository is changed in this way: If it finds V6 instances like org.opensearch.security.securityconf.impl.v6.RoleV6, it auto-converts these to V7 instances like org.opensearch.security.securityconf.impl.v7.RoleV7. The V7 classes already have functionality for that which is already used for the securityadmin migration command.
3. This makes the distinction of V6/V7 on all layers below unnecessary. DynamicConfigFactory does no longer need a distinction between two config versions.
4. ConfigModelV6 becomes redundant.
5. As PrivilegeEvaluator consumes the super interface ConfigModel, it does not notice anything about this change.

• Category: Refactoring

• Why these changes are required? - Minimize duplicate logic for privilege evaluation

• What is the old behavior before changes and new behavior after changes? - none

• Category: Refactoring

• Why these changes are required? - Minimize duplicate logic for privilege evaluation

• What is the old behavior before changes and new behavior after changes? no behavior changes

Issues Resolved

• Partially solves [RFC] Retire support for V6 configuration #4493

Testing

• New int test LegacyConfigV6AutoConversionTest

Check List

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

By submitting this pull request, I confirm that my contribution is made under the terms of the Apache 2.0 license.
For more information on following Developer Certificate of Origin and signing off your commits, please check here.

[codecov]

Codecov Report

Attention: Patch coverage is 72.84345% with 85 lines in your changes missing coverage. Please review.

Project coverage is 64.53%. Comparing base (f353b0e) to head (ade7c8a).

Files with missing lines	Patch %	Lines
...ch/security/securityconf/DynamicConfigFactory.java	60.00%	9 Missing and 7 partials ⚠️
...ecurityconf/impl/SecurityDynamicConfiguration.java	77.41%	9 Missing and 5 partials ⚠️
...earch/security/configuration/ConfigurationMap.java	67.74%	7 Missing and 3 partials ⚠️
...rg/opensearch/security/securityconf/Migration.java	67.85%	8 Missing and 1 partial ⚠️
...a/org/opensearch/security/tools/SecurityAdmin.java	0.00%	8 Missing ⚠️
...g/opensearch/security/securityconf/impl/CType.java	89.85%	5 Missing and 2 partials ⚠️
...n/java/org/opensearch/security/tools/Migrater.java	0.00%	6 Missing ⚠️
...ty/configuration/ConfigurationLoaderSecurity7.java	66.66%	4 Missing and 1 partial ⚠️
...a/org/opensearch/security/DefaultObjectMapper.java	33.33%	3 Missing and 1 partial ⚠️
...ecurity/configuration/ConfigurationRepository.java	80.95%	2 Missing and 2 partials ⚠️
... and 1 more

Additional details and impacted files

@@            Coverage Diff             @@
##              2.x    #4753      +/-   ##
==========================================
- Coverage   65.38%   64.53%   -0.85%     
==========================================
  Files         317      318       +1     
  Lines       22182    22289     +107     
  Branches     3584     3596      +12     
==========================================
- Hits        14504    14385     -119     
- Misses       5881     6133     +252     
+ Partials     1797     1771      -26     

Files with missing lines	Coverage Δ
...arch/security/dlic/rest/api/AbstractApiAction.java	82.81% <100.00%> (-0.14%)	⬇️
...earch/security/dlic/rest/api/AccountApiAction.java	60.56% <ø> (ø)
.../security/dlic/rest/api/ActionGroupsApiAction.java	78.18% <ø> (ø)
...rch/security/dlic/rest/api/AllowlistApiAction.java	89.47% <ø> (ø)
...nsearch/security/dlic/rest/api/AuditApiAction.java	90.76% <ø> (ø)
...curity/dlic/rest/api/AuthTokenProcessorAction.java	90.90% <ø> (ø)
.../security/dlic/rest/api/CertificatesApiAction.java	35.13% <ø> (ø)
...security/dlic/rest/api/ConfigUpgradeApiAction.java	72.97% <100.00%> (ø)
...ch/security/dlic/rest/api/FlushCacheApiAction.java	65.38% <ø> (ø)
...security/dlic/rest/api/InternalUsersApiAction.java	76.85% <ø> (ø)
... and 29 more

... and 7 files with indirect coverage changes