refactor: item management data layers

[uutkukorkmaz]

Overview

This issue addresses multiple problems identified in the item system, such as #180, #191, #192, #193, and many unknown ones. The goal is to refactor the item management data layer to resolve these issues while adhering to project standards and meeting expected behavior.

Objectives

• Enhance Performance: Optimize data storage and retrieval to minimize response times and reduce server load. Improve caching mechanisms and streamline database queries to handle large-scale operations more efficiently.
• Improve Maintainability: Simplify the overall structure by breaking down complex functionalities into smaller, well-documented components. The code should be easier to understand, debug, and modify for future developers.
• Increase Scalability: Design the system to handle increased user traffic and data volume without significant performance degradation. Utilize load balancing and horizontal scaling strategies to ensure stability under heavy loads.
• Ensure Code Quality: Follow established coding standards and best practices to enhance readability and consistency across the codebase.
• Strengthen Testing: Build comprehensive unit tests (also introducing mutation testing would be a nice-to-have) to cover all critical functions, ensuring that changes don’t introduce new bugs or regressions.
• Ensure Flexibility: Use a modular, loosely-coupled architecture to allow future features to be easily integrated. This will ensure the system can evolve with new requirements without major rewrites or disruptions.