Create unit test project for WeatherApp and update WeatherService tests

[sweep-ai[bot]]

Description

This PR adds a new unit test project for the WeatherApp application and updates the tests for the WeatherService class. The changes include:

• Created a new project file "WeatherAppWebApi.Tests.csproj" in the "WeatherApp/Backend/WeatherApp/WeatherAppWebApi.Tests" directory.
• Modified the solution file "WeatherApp.sln" to include the new test project.
• Updated the test class "WeatherServiceTests.cs" in the "WeatherApp/Backend/WeatherApp/WeatherAppWebApi.Tests" directory to include unit tests for the WeatherService class.
• Changed the testing framework from MSTest to NUnit.
• Updated the target framework of the test project to .NET 7.0.

Summary of Changes

• Added a new unit test project "WeatherAppWebApi.Tests.csproj" with .NET 7.0 and NUnit as the testing framework.
• Updated the solution file "WeatherApp.sln" to include the new test project.
• Updated the test class "WeatherServiceTests.cs" to include unit tests for the WeatherService class.
• Changed the testing framework from MSTest to NUnit.
• Updated the target framework of the test project to .NET 7.0.

Fixes #1.

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[sweep-ai[bot]]

GitHub actions yielded the following error.

The command that failed is dotnet build --no-restore WeatherApp.sln. Here are the relevant lines from the logs:

##[error]/home/runner/work/RanodmVuePractice/RanodmVuePractice/WeatherApp/Backend/WeatherApp/WeatherAppWebApi.Tests/WeatherServiceTests.cs(1,7): error CS0246: The type or namespace name 'Moq' could not be found (are you missing a using directive or an assembly reference?) [/home/runner/work/RanodmVuePractice/RanodmVuePractice/WeatherApp/Backend/WeatherApp/WeatherAppWebApi.Tests/WeatherAppWebApi.Tests.csproj]
##[error]/home/runner/work/RanodmVuePractice/RanodmVuePractice/WeatherApp/Backend/WeatherApp/WeatherAppWebApi.Tests/WeatherServiceTests.cs(11,17): error CS0246: The type or namespace name 'Mock<>' could not be found (are you missing a using directive or an assembly reference?) [/home/runner/work/RanodmVuePractice/RanodmVuePractice/WeatherApp/Backend/WeatherApp/WeatherAppWebApi.Tests/WeatherAppWebApi.Tests.csproj]

This is likely a linting or type-checking issue with the source code. Update the code the changes and avoid modifying the existing tests.

I'm getting the same errors 3 times in a row, so I will stop working on fixing this PR.