Refactor to encapsulate Recommender logic in the RecommenderPackageFeed

[jebriede]

Bug

Fixes: https://github.com/NuGet/Client.Engineering/issues/2530

Description

This refactoring focuses on improving the encapsulation and separation of concerns within the recommender logic for package feeds. The main objective is to move the logic related to the recommender feed from the generalized search object to a specialized recommender feed, thereby simplifying the code and reducing technical debt.

Key Changes:

• Encapsulation of Recommender Logic: The recommender logic is moved from the search object to a dedicated recommender feed, which now decorates the main feed. This change ensures that the search object no longer needs to handle the intricacies of the recommender logic.
• Simplification of Search Object: The search object now operates on a single feed instead of handling multiple feeds (main feed and recommender feed). This reduces complexity and potential errors.
• Deduplication and Combination of Results: The deduplication of package results from the main feed and the recommender feed is now handled within the recommender feed using a more concise approach with LINQ.
• Private Methods and Internal Logic: Several methods that were previously public and exposed have been made private to encapsulate the logic within the recommender feed.

Benefits:

This refactoring significantly improves code maintainability by isolating the recommender logic, making the codebase easier to understand and manage, and reducing the cognitive load on developers, allowing them to focus on the core responsibilities of the search object without distraction, thereby setting the stage for future enhancements and features.

PR Checklist

• Meaningful title, helpful description and a linked NuGet/Home issue
• Added tests
• Link to an issue or pull request to update docs if this PR changes settings, environment variables, new feature, etc.

[jgonz120]

Looks good to me! This change definitely feels like it simplifies the code and makes it easier to understand :)

[jeffkl]

A pattern I prefer is to make a private constructor with a static instance to ensure that no one makes extra instances of this

Suggested change

	{
	{
	public static IdentityIdEqualityComparer Instance = new IdentityIdEqualityComparer();
	private IdentityIdEqualityComparer()
	{
	}

Then line 26 can go away and line 107 can use the static singleton

[jebriede]

I like this a lot, thanks!

[nkolev92]

This needs to be OrdinalIgnoreCase.