This issue addresses a needed refactoring on how we're currently linking Sponsorship objects to SponsorshipPackage. For some forgotten reason, the initial database modeling doesn't implement a foreign key from the first to the second model but only introduced a level_name attribute which holds a copy of the package name at the moment of the sponsorship creation, as you can see here.

This wasn't a problem until we start to introduce more complex logic on the sponsors app such as conditional logo placement (#1822) and more tier quantities for benefits (#1826). Both features depends on checking if a Sponsorship belongs to a certain SponsorshipPackage to do stuff. Both PRs are relying on top of the level_name attribute but this checking is problematic since string comparison are way more unstable than using foreign key to check against objects.

The refactoring touches:

• Add a package FK from the Sponsorship model to the SponsorshipPackage;
• Data migration to populate the new FK for existing sponsors based in the level_name attribute;
• Update the sponsorships creation to populate the new FK;
• Update sponsorship admin + approval process;
• Refactor list_sponsors template tag to use the package instead of name to control the logo dimensions (maybe adding a new attribute to the package itself to store this data?);
• Refactor TieredQuantityConfiguration.get_benefit_feature_kwargs to replace level_name by the new FK;