docs: update endpoints to use file-routing approach (#5397)

- Move the original guides for creating endpoints and middlewares to sub-sections in the Endpoints category.
- Replace existing guides for endpoints and middlewares with the new approach.
- Update all endpoints-related snippets across docs to use this new approach.

www/apps/docs/content/modules/multiwarehouse/backend/create-inventory-service.md

@@ -19,7 +19,7 @@ This guide will only explain what is required to create in your custom inventory
 
 :::note
 
-It should be noted that the Medusa backend expects the inventory module to have entities for an inventory item, an inventory level, and a reservation item, as it uses the IDs of those entities when orchestrating between different modules and the in the endpoints it exposes. You can learn more about this in the [Inventory Module Architecture documentation](../inventory-module.md).
+It should be noted that the Medusa backend expects the inventory module to have entities for an inventory item, an inventory level, and a reservation item, as it uses the IDs of those entities when orchestrating between different modules and the in the API Routes it exposes. You can learn more about this in the [Inventory Module Architecture documentation](../inventory-module.md).
 
 :::
 

www/apps/docs/content/modules/multiwarehouse/backend/create-stock-location-service.md

@@ -19,7 +19,7 @@ This guide will only explain what is required to create in your custom stock loc
 
 :::note
 
-It should be noted that the Medusa backend expects the stock location module to have entities for a location and a location address, as it uses the IDs of those entities when orchestrating between different modules and the in the endpoints it exposes. You can learn more about this in the [Stock Location Module Architecture documentation](../stock-location-module.md).
+It should be noted that the Medusa backend expects the stock location module to have entities for a location and a location address, as it uses the IDs of those entities when orchestrating between different modules and the in the API Routes it exposes. You can learn more about this in the [Stock Location Module Architecture documentation](../stock-location-module.md).
 
 :::