Some actions are missing in delete() method of AbstractEngine class

[psam44]

In AbstractEngine.ts, create() takes care of the index creation with createEngineIndex() and of the config collection creation with engineConfigManager.createCollection().

BUT, in delete(), there are no such reverse actions, to delete the config collection and finally the index itself.

version 1.2.0.

[rolljee]

This is tricky and must be discussed in house, because deleting a index can result in deleting things that have been created by other plugins and thus, this can be destructive for the application.