CreateCustomer handler for creating a new customer.

CreateInventory handler for creating a new inventory.

CreateItem handler for creating a new item.

CreateUser creates a new user.

DefaultRoute handler for the root endpoint.

DeleteUser deletes a user by ID.

GetCustomersItems handler to fetch all inventories and their items for customers.

GetInventories handler to fetch all inventories.

GetItems handler to fetch all items.

GetUser retrieves a user by ID.

GetUsers retrieves all users.

NotFoundRoute handler for undefined routes.

SetupRoutes defines all the routes for the application.

UpdateUser updates a user by ID.