CMS: Fix tag & marked item filtering on blogposts

[EngincanV]

This pull request refactors and improves the filtering logic in the EfCoreBlogPostRepository for both the GetCountAsync and GetListAsync methods. The main focus is on making the filtering for tag and favorite user IDs more robust and efficient, as well as simplifying the code by removing unnecessary variables and checks.

Filtering and Query Improvements:

• Updated the filtering logic for tagId and favoriteUserId to ensure only valid GUIDs are used, preventing potential runtime errors from invalid IDs. Now, the code filters and parses IDs in one step using Where(x => Guid.TryParse(x, out _)).Select(Guid.Parse).ToList(). [1] [2]
• Changed the default values for filtered entity ID lists to empty lists ([]) instead of null, and updated the query conditions to check for .Count > 0 instead of null checks. This simplifies the logic and avoids null reference issues. [1] [2]

Code Simplification:

• Removed unused variables and redundant code, such as the entityIdFilters variable and unnecessary calls to ToString() on GUIDs in query filters. [1] [2]
• Streamlined the return statement in GetCountAsync by returning the result of CountAsync directly.

[Copilot]

Pull Request Overview

This pull request refactors the filtering logic in the EfCoreBlogPostRepository to improve robustness and efficiency when handling tag and favorite user ID filtering for blog posts.

• Implements safer GUID parsing with validation using Guid.TryParse before conversion
• Replaces null checks with empty list initialization and count-based conditions
• Removes redundant code and unused variables to simplify the implementation

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