feat: updates with relations, feat: updating products in collections, fix: corrections in relations

[uro]

Updated services to handle product collections and products in Strapi; also fixed some other major bugs.

Major changes:

In the update-strapi.ts file:

• Reverted "relation" comments from product updates.
• Added a new method, updateProductsWithinCollectionInStrapi, to update products within a collection in Strapi when they're added or removed from collections.
• Added a private method adjustProductAndUpdateInStrapi to decouple product adjusting as it's now shared by two methods - there is an edge case in naming created by the Medusa team.
• Updated the translateDataToStrapiFormat method to translate underscores in relation names to dashes for consistency globally.

In the strapi.ts file:

• Added event subscribers for the PRODUCTS_ADDED and PRODUCTS_REMOVED events of the ProductCollectionService.
• Implemented logic to update products within a collection in Strapi when products are added or removed.

In the schema.json files:

• There was a bug in the relation between product and product collections. This prevented it from populating the data.
• Updated the product and product-collection schema to change the relationship type from manyToMany to oneToMany and similarly in the product schema.

In the utils.js file:

• Used attachOrCreateStrapiIdFromMedusaId function in the Update controller to handle nested relations

These changes enhance the functionality of the Medusa Plugin for Strapi by better handling product collections, products in the Strapi backend and to bring back the "nested update" functionality.