* Renamed the language item controllers to follow the current standard (they should not be called "entity")
* Renamed the webhook item controllers to follow the current standard (they should not be called "entity")
* Moved the webhook item controllers to the "/item" silo
* Renamed the user gorup controller base to be singular instead of plural
* Create member group endpoint should yield a 201 created response
* Update member endpoint should yield an empty 200 OK upon success
* Update UpdateUserDataController with correct action name and return an empty 200 OK upon success
* More item endpoints alignment
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Co-authored-by: Elitsa <elm@umbraco.dk>
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