Add unit tests for DateRequestHandler

[Copilot]

DateRequestHandler had no unit test coverage. Adds tests targeting the single Handle method to cover both the success and failure paths through the IApiClient.GetComparisonDates delegation.

New tests — RequestHandlers/DateRequestHandlerTests.cs

• Handle_ReturnsSuccess_WhenApiClientSucceeds — verifies the success result and data is forwarded as-is from the API client
• Handle_ReturnsFailure_WhenApiClientFails — verifies failure propagation without transformation

Both tests assert the API client is called exactly once via Verify.

Warning

Firewall rules blocked me from connecting to one or more addresses (expand for details)

I tried to connect to the following addresses, but was blocked by firewall rules:

• f.feedz.io
  • Triggering command: /usr/bin/dotnet dotnet test EstateManagementUI.BlazorServer.Tests/EstateManagementUI.BlazorServer.Tests.csproj --filter DateRequestHandlerTests (dns block)
  • Triggering command: /opt/hostedtoolcache/CodeQL/2.24.0/x64/codeql/csharp/tools/linux64/Semmle.Autobuild.CSharp /opt/hostedtoolcache/CodeQL/2.24.0/x64/codeql/csharp/tools/linux64/Semmle.Autobuild.CSharp (dns block)
  • Triggering command: /usr/bin/dotnet dotnet restore --no-dependencies /home/REDACTED/work/EstateManagementUI/EstateManagementUI/EstateManagementUI.sln --packages /home/REDACTED/work/EstateManagementUI/.codeql-scratch/dbs/csharp/working/packages /p:DisableImplicitNuGetFallbackFolder=true --verbosity normal /p:TargetFrameworkRootPath=/home/REDACTED/work/EstateManagementUI/.codeql-scratch/dbs/csharp/working/emptyFakeDotnetRoot /p:NetCoreTargetingPackRoot=/home/REDACTED/work/EstateManagementUI/.codeql-scratch/dbs/csharp/working/emptyFakeDotnetRoot /p:AllowMissingPrunePackageData=true (dns block)

If you need me to access, download, or install something from one of these locations, you can either:

• Configure Actions setup steps to set up my environment, which run before the firewall is enabled
• Add the appropriate URLs or hosts to the custom allowlist in this repository's Copilot coding agent settings (admins only)

Original prompt

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This section details on the original issue you should resolve

<issue_title>DateRequestHandler Unit Tests</issue_title>
<issue_description></issue_description>

<agent_instructions>Ensure a good level of code coverage as close to 100% as possible</agent_instructions>

Comments on the Issue (you are @copilot in this section)

• Fixes DateRequestHandler Unit Tests #781

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