Refactor FluentExtensions.Switch to use equality comparers instead of requiring IEquatable<T> implementation

[ric15ni]

Proposed changes

• In Louis.Fluency.FluentExtensions.Switch, use EqualityComparer<T>.Default instead of requiring that values being compared implement IEquatable<T>. This will allow enums to be used as values and comparands. Enums do not implement IEquatable<T> for compatibility reasons, as they predate generics.
• Add FluentExtensions.Switch overloads that let the user specify an IEqualityComparer<T> interface.

Checklist of related issues / discussions

As the issue with FluentExtensions.Switch not working with enums surfeced in production while on a strict deadline, there was unfortunately no time to open a proper issue.

Types of changes

This pull request introduces the following types of changes:

• Bug fix
• New feature
• Test addition / update (no changes to non-test code)
• Refactor (no changes in public API syntax or semantics)
• Performance improvement (no changes in public API syntax or semantics)
• Documentation (docs directory) update
• Dependency addition / update
• Changes to the build scripts
• Changes to CI (workflows, bot / app configurations)
• Changes to repository files (.gitattributes, .gitignore)
• Other

Breaking changes

This pull request introduces breaking changes:

• Yes
• No (a restriction has been lifted on a type parameter in some methods; existing code will show no change in behavior, save for a negligible performance hit)

Checklist

• For all types of changes:
  • I have read the Code of Conduct and agree to be bound by it
  • I have read the Contributor Guide and agree to follow it
• For code changes only:
  • The project builds on my machine, via the provided build script, with zero warnings
  • I have added tests that prove my feature works / my fix is effective
  • I have added / modified XML documentation according to changes in code
  • I have checked that all the links I added or modified in XML documentation point to their intended destination
• For documentation changes (docs directory) only:
  • I have built and tested documentation locally
  • I have checked that all the links I added or modified point to their intended destination

[rdeago]

LGTM 👍