Adds missing XML comments and made sink backing field private

[alefranz]

This PR adds missing XML comments to improve code documentation and refactors the access modifier of a sink backing field to enhance encapsulation.

• Updated XML documentation for constructors, properties, and extension methods
• Changed the accessibility of the sink backing field from public to private
• Added pragma directives to suppress obsolete warnings in a controlled manner

[Copilot]

Pull Request Overview

This PR adds missing XML comments to improve code documentation and refactors the access modifier of a sink backing field to enhance encapsulation.

• Updated XML documentation for constructors, properties, and extension methods
• Changed the accessibility of the sink backing field from public to private
• Added pragma directives to suppress obsolete warnings in a controlled manner

Reviewed Changes

Copilot reviewed 4 out of 4 changed files in this pull request and generated 1 comment.

File	Description
src/MELT/TestLoggerProvider.cs	Made the sink backing field private and added XML comments for constructors
src/MELT/Helpers/MELTLoggingBuilderExtensions.cs	Added XML documentation and updated obsolete attribute messages for extension methods
src/MELT/Helpers/LogEntry.cs	Added XML comments to clarify usage of the obsolete property
src/MELT/Helpers/BeginScope.cs	Wrapped obsolete usage with pragma directives to suppress warnings

Comments suppressed due to low confidence (1)

src/MELT/Helpers/MELTLoggingBuilderExtensions.cs:27

• [nitpick] The obsolete message is lengthy and concatenated, which may reduce readability. Consider refactoring the message into a clearer, more maintainable format.

[Obsolete("The recommended alternative is " + nameof(AddTest) + "(Action<" + nameof(TestLoggerOptions) + ">) or use the simplified factory.WithWebHostBuilder(builder => builder.UseTestLogging()). The sink can then be retrieved with factory.GetTestLoggerSink()")]