* Rework language service and API
* Revert unintended commit of Directory.Build.props
* Create OS conditional test for invalid ISO codes
* Reintroduce and obsolete old Delete method on ILocalizationService + make new Delete method delete by ISO code + add obsoletion attrs to service implementation
* Review comments + utilize new Delete method
* Do not allow model reuse when creating a new language
* Fix bad merge
* Split localization service into dedicated services for language and dictionary item handling
* Replaced ILocalizationService usage in management API (as much as can be done for now)
* Ensure we can create dictionary items with explicit keys (but no duplicates)
* Fix culture controller so it works properly with pagination
* Update OpenAPI JSON
* Actually update the language being updated...
* Unit test for invalid ISO now no longer needs to differ between OS :)
* A little bit of code health improvements
* A litte less code duplication
* Remove duplicate validation
