feat: add global OpenSearch index prefix support (#8489)

[mezzeddinee]

Fixes #8489 by introducing index prefixing as a global OpenSearch setting and removing MonitoringDB-local prefix handling.

What changed

• src/DIRAC/ConfigurationSystem/Client/Utilities.py

  • Read /Systems/NoSQLDatabases/IndexPrefix in getElasticDBParameters.
  • Normalize value (strip().lower()) and pass it as IndexPrefix.

• src/DIRAC/Core/Base/ElasticDB.py

  • Read global IndexPrefix from DB parameters.
  • Forward it to ElasticSearchDB as globalIndexPrefix.

• src/DIRAC/Core/Utilities/ElasticSearchDB.py

  • Added globalIndexPrefix constructor parameter and property setter.
  • Added _withGlobalPrefix() helper to prepend the global prefix to index names/patterns.
  • Applied prefixing across index/template/search/read/write/delete operations.
  • Refactored bulk_index flow to avoid apparent double-prepending.

• src/DIRAC/MonitoringSystem/DB/MonitoringDB.py

  • Removed MonitoringDB-specific IndexPrefix lookup from CS.
  • Rely on inherited global prefix mechanism via ElasticDB.

• docs/source/AdministratorGuide/ExternalsSupport/index.rst

  • Documented IndexPrefix under Systems/NoSQLDatabases and clarified it is lower-case.

• docs/source/AdministratorGuide/Systems/MonitoringSystem/index.rst

  • Updated docs to reference global Systems/NoSQLDatabases/IndexPrefix.

• src/DIRAC/Core/scripts/install_full.cfg

  • Added commented example for global IndexPrefix under NoSQLDatabases.

• src/DIRAC/Core/Utilities/test/Test_ElasticSearchDB.py

  • Added and updated unit tests to verify expected index names across ElasticSearchDB interactions when a global index prefix is configured.

[aldbr]

Note: @mezzeddinee if you updated your PR and you want a reviewer having another look at it, please mark it as "Ready for review", cheers

[mezzeddinee]

Note: @mezzeddinee if you updated your PR and you want a reviewer having another look at it, please mark it as "Ready for review", cheers
Addressed all requested changes in 8a86d4d (docs lower-case note, globalIndexPrefix property, removed list/tuple branch, bulk_index double-prefix fix). PR is now ready for re-review.

[fstagni]

Would you try and write (or expand) a unit test to make sure that the index names are the expected ones, on every interaction?

This is quite delicate and have been bitten by this before.

[aldbr]

Is it ready to be reviewed @mezzeddinee?

[mezzeddinee]

I added/expanded ElasticSearchDB unit tests for global index prefix behavior, and they pass locally. Current remaining failure appear perhaps unrelated to this change: DiracX Unit Tests failing in CI setup (pixi add local file:// path resolution).

Any guidance on these CI issues is appreciated.