feature: expose elasticsearch to plugins

[ClemDoum]

Changes

Changed

• expose elasticsearch utils to plugin by adding it to the Api class

[ClemDoum]

Closing this one waiting for a deeper refacto leveraging dependencies injection

[caro3801]

Reopening after the changes: Elastic search client methods are available through the API using dependency injection so there is only one entry point to get to elastic search instance (instead of imports). In tests, is esConnectionHelper the datashare plugin has been added to access custom methods