#27979 New lang vars endpoint and findAllVariables methods

[fabrizzio-dotCMS]

Proposed Changes

• The main goal of this PR is to introduce the new methods that will be used to replace the old Language Keys stored as property files
• These methods have been added to LanguageVariableAPI
• The new methods are designed to simply return the LanguageVariables no user or permission is contemplated here.
• Even though there were a few other methods here designed to return KeyValue objects these have a problem with being index dependant
• These LanguageVariables are cached using the same LanguageCache but a separate group. All the Language Variables are cached per language. so if we update or unpublish a LanguageVariable let's say (and cache invalidation is needed) This will not affect other LanguageVaribales of a different language living cache.
• A new Endpoint for retrieving LanguageVariables has been added.
• The respective postman test was added too.
• Changes were made to ESContentletAPIImpl so the respective cache invalidation can be accomplished.
• Several issues were outlined on ESContentletAPIImpl by sonar so they were corrected.

[spbolton]

Could you reslove the 8 new issues showing in Sonarqubue mostly repeated contestants and assert parameters the wrong way around.
they should also show in IntelliJ if you have sonar lint enabled,
and pulling out the repeated strings should be easy if you right click and use the IntellJ Refactor -> Introduce Constant option. https://sonarqube.dotcms.site/project/issues?id=dotCMS_core_AYSbIemxK43eThAXTlt-&pullRequest=28429&resolved=false

[fabrizzio-dotCMS]

Could you reslove the 8 new issues showing in Sonarqubue mostly repeated contestants and assert parameters the wrong way around. they should also show in IntelliJ if you have sonar lint enabled, and pulling out the repeated strings should be easy if you right click and use the IntellJ Refactor -> Introduce Constant option. https://sonarqube.dotcms.site/project/issues?id=dotCMS_core_AYSbIemxK43eThAXTlt-&pullRequest=28429&resolved=false

done @spbolton

[dotcms-sonarqube]

Quality Gate passed

Issues
5 New issues
25 Fixed issues
0 Accepted issues

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

See analysis details on SonarQube

Talked to Steve. He is aware that modifying EContentletAPIImpl to apply soanr feedback always makes sonrar detect more problems and request more changes