Performance: Implement key-based caching for data type and template repositories

[AndyButland]

Description

We currently have nested repositories for reading documents and media by GUID, that are aligned with the main repository to ensure that if a request is made by Id, it's cached by key, and vice versa (see #21124).

Whilst this may not be architecturally ideal, it does follow an existing and established pattern, so seems reasonable in advance of more significant repository refactoring.

In practice, this didn't show any obvious improvement in save/publish time, but nonetheless feels a sensible update to make to ensure these requests for data types and templates are cached however they are retrieved.

In working on this PR I verified that this is already in place for content types, as we have policy there of retrieving all and caching them, so by ID/key look-ups always come from this already cached collection.

Change Details

• Implements GUID key caching for DataTypeRepository and TemplateRepository to improve lookup performance
• When entities are retrieved by int ID, they are also cached for GUID lookups (and vice versa)
• Adds comprehensive tests verifying caching behavior for content types, data types, and templates

Testing

Integration tests have been added to verify the behaviour:

• Verify that retrieving a data type by ID then by GUID does not hit the database on the second call
• Verify that retrieving a template by ID then by GUID does not hit the database on the second call
• Verify existing content type caching behaviour is already correct

[Copilot]

Pull request overview

This PR implements GUID key caching for DataTypeRepository and TemplateRepository to improve lookup performance by ensuring entities are cached for both int ID and GUID lookups bidirectionally.

Key changes:

• Adds nested read repositories (TemplateByGuidReadRepository and DataTypeByGuidReadRepository) following the existing pattern used in DocumentRepository and MediaRepository
• Implements bidirectional cache population where retrieving by ID also caches by GUID and vice versa
• Adds comprehensive integration tests verifying the caching behavior for all three repository types (templates, data types, and content types)

Reviewed changes

Copilot reviewed 7 out of 7 changed files in this pull request and generated 2 comments.

Show a summary per file

File	Description
src/Umbraco.Infrastructure/Persistence/Repositories/Implement/TemplateRepository.cs	Adds nested TemplateByGuidReadRepository for GUID lookups, implements cache population in PerformGet, PerformGetAll, and Save, includes obsolete constructor for backward compatibility
src/Umbraco.Infrastructure/Persistence/Repositories/Implement/DataTypeRepository.cs	Adds nested DataTypeByGuidReadRepository for GUID lookups with database queries, implements bidirectional cache population methods, updates Get(Guid) to use new repository
src/Umbraco.Core/Persistence/Repositories/ITemplateRepository.cs	Adds Get(Guid key) method with default implementation throwing NotImplementedException
tests/Umbraco.Tests.Integration/Umbraco.Infrastructure/Persistence/Repositories/TemplateRepositoryTest.cs	Adds five new integration tests verifying caching behavior for ID and GUID lookups in various scenarios
tests/Umbraco.Tests.Integration/Umbraco.Infrastructure/Persistence/Repositories/DataTypeRepositoryTest.cs	New test file with five integration tests mirroring template repository tests for data types
tests/Umbraco.Tests.Integration/Umbraco.Infrastructure/Persistence/Repositories/ContentTypeRepositoryTest.cs	Adds four integration tests documenting existing caching behavior, adds helper dependencies, adds CreateRepository method
tests/Umbraco.Tests.Common/Builders/DataTypeBuilder.cs	Updates default creator ID to use constant Constants.Security.SuperUserId instead of hardcoded 1