T2856 inconsistent logic for duplicate donations in cart & missing aggregation

[Shayan105]

Summary

Note: In the the Task description @ecino chose the option A.

This PR Fixes the following problems :

Issues

1. When a user takes multiple time the same product (and potentially to the same child), a new line in the cart was created.
2. Once a user added a product in the cart, they cannot longer see it in the gift/fund proposition

Fixes

1. The 1st issue is solved by aggregating the amount of the product.
2. For the 2nd just remove a filter.

[gemini-code-assist]

Summary of Changes

Hello @Shayan105, I'm Gemini Code Assist¹! I'm currently reviewing this pull request and will post my feedback shortly. In the meantime, here's a summary to help you and other reviewers quickly get up to speed!

This pull request refines the donation cart functionality and product display. It introduces aggregation for identical donations, preventing multiple cart lines for the same item and recipient, and resolves an issue where products already added to the cart were hidden from the gift/fund proposition page, thereby enhancing the user's ability to manage and select donations.

Highlights

• Cart Aggregation Logic: Implemented logic in the donation_new method to aggregate the amount of duplicate donations for the same product and recipient into a single cart line, rather than creating new lines.
• Gift/Fund Proposition Visibility: Removed a filter in my2_render_add_a_gift_page that previously prevented products already in the cart from being displayed in the gift/fund proposition list, ensuring all options are visible.

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[gemini-code-assist]

Code Review

This pull request correctly addresses the aggregation of duplicate donations in the cart and ensures products remain visible in the gift/fund list after being added to the cart. The implementation is mostly sound, but I've identified a critical issue where donations with different frequencies (e.g., one-time vs. monthly) could be incorrectly merged. I've provided a fix for this. Additionally, I've included a couple of suggestions to enhance code readability and performance.

[Shayan105]

/gemini review

[gemini-code-assist]

Code Review

This pull request aims to fix two issues: aggregating duplicate donations in the cart and ensuring products remain visible after being added. The implementation for aggregating donations is a good step forward, and removing the product filter is the correct approach given the new aggregation logic. However, my review has identified a critical issue in the aggregation logic that could lead to incorrect behavior by merging one-time and monthly donations. I've also found a performance issue where database operations are performed inside a loop, and I've provided a more efficient alternative. Lastly, there's a minor suggestion to improve code readability. Addressing these points will make the solution robust and performant.