Refactoring: Add extension method for retrieval of language ISO codes if that's all we need

[AndyButland]

Description

There are a number of places where we retrieve all languages from the database, when we only need all ISO codes.

This PR introduces a new method that will only retrieve that field from the database, and uses it wherever we currently get all languages just to select only the ISO code field.

So a small optimization to reduce the amount of data we pull from the database.

[Copilot]

Pull Request Overview

This PR introduces a performance optimization by adding a new method GetAllIsoCodesAsync() that retrieves only ISO culture codes from the database instead of full language objects when that's all that's needed.

• Adds GetAllIsoCodesAsync() method to the language service and repository
• Updates multiple locations that were fetching full language objects just to extract ISO codes
• Includes comprehensive test coverage for the new functionality

Reviewed Changes

Copilot reviewed 14 out of 15 changed files in this pull request and generated 2 comments.

Show a summary per file

File	Description
src/Umbraco.Core/Services/ILanguageService.cs	Adds interface definition for GetAllIsoCodesAsync() with default implementation and documentation improvements
src/Umbraco.Core/Services/LanguageService.cs	Implements GetAllIsoCodesAsync() method that delegates to repository
src/Umbraco.Core/Persistence/Repositories/ILanguageRepository.cs	Adds GetAllIsoCodes() method interface with default implementation
src/Umbraco.Infrastructure/Persistence/Repositories/Implement/LanguageRepository.cs	Implements optimized database query to fetch only ISO codes
tests/Umbraco.Tests.Integration/Umbraco.Infrastructure/Services/LanguageServiceTests.cs	Adds integration test for new GetAllIsoCodesAsync() method
src/Umbraco.Core/Services/ContentValidationServiceBase.cs	Updates to use new optimized method
src/Umbraco.Core/Services/ContentPublishingService.cs	Updates two locations to use new optimized method
src/Umbraco.Core/Services/ContentEditingService.cs	Updates to use new optimized method
src/Umbraco.Core/Routing/UrlProviderExtensions.cs	Updates to use new optimized method
src/Umbraco.Core/Routing/PublishedUrlInfoProvider.cs	Updates to use new optimized method
src/Umbraco.Cms.Api.Management/Factories/UserGroupPresentationFactory.cs	Refactors to use existing GetIsoCodesByIdsAsync() method instead of fetching all languages
src/Umbraco.Cms.Api.Management/Factories/DictionaryPresentationFactory.cs	Updates to use new optimized method
src/Umbraco.Examine.Lucene/BackOfficeExamineSearcher.cs	Updates to use new optimized method
tests/Umbraco.Tests.Integration/Umbraco.Examine.Lucene/UmbracoExamine/ExamineExternalIndexSearcherTest.cs	Updates to use new optimized method

[kjac]

@AndyButland I like the syntax change throughout the code changes, where (await _languageService.GetAllAsync()).Select(language => language.IsoCode) becomes await _languageService.GetAllIsoCodesAsync().

However, well intended as this is, it actually incurs a performance penalty if I'm not entirely mistaken.

LanguageService.GetAllAsync() calls LanguageRepository.GetMany(), which is an implementation on EntityRepositoryBase that utilizes the repository cache policy. The language repo provides a FullDataSetRepositoryCachePolicy, so all LanguageDto entities is likely cached by the time anyone attempts to read out all languages from the language service.

The new GetAllIsoCodesAsync() in LanguageService goes straight to the DB to fetch ISO codes.

Like I said, the syntax change is nice. Would it make sense to retain the default implementation of GetAllIsoCodesAsync() in ILanguageService, and remove the implementation in LanguageService? The default implementation uses GetMany(), so it won't hit the DB unless the cache is cleared.

Another alternative would be to implement GetAllIsoCodesAsync() as an extension method for ILanguageService. This might make it clearer what's going on caching wise.

[AndyButland]

Ah yes, that's a good point @kjac - thanks for catching that and apologies for the oversight. I've followed your extension method suggestion. So no performance improvement now, but likely worth having the syntax improvement as you suggest.

[kjac]

Looks good 💪