feat: added product level fields to product type attributes

[demeyerthom]

This pull request introduces support for an attribute level field in product types, enhances the Taskfile.yml with additional commands, and adds new validation and utility functions. The most significant changes focus on the implementation and testing of the new attribute level functionality, ensuring compatibility and validation throughout the codebase.

Product Type Attribute Level Support:

• Added a new level field to the product type attributes in commercetools/resource_product_type.go, allowing specification of whether an attribute is defined at the product or variant level. This includes validation to restrict values to AttributeLevelEnumProduct or AttributeLevelEnumVariant. [1] [2]
• Updated attribute-related functions (flattenProductTypeAttributes, resourceProductTypeAttributeChangeActions, and expandProductTypeAttributeDefinitionItem) to handle the new level field. Validation prevents changing the level of an existing attribute. [1] [2] [3]

Testing Enhancements:

• Extended tests in commercetools/resource_product_type_test.go to include scenarios for the new level field, ensuring proper functionality for both product-level and variant-level attributes. Added a new test case TestAccProductTypes_ProductVariant to validate attribute level changes and error handling. [1] [2]
• Updated test data structures and configurations to accommodate the new level field. [1] [2]

Taskfile Enhancements:

• Added a default task to Taskfile.yml for listing all tasks and included terraform fmt in the format task for recursive formatting of example files. [1] [2]

Utility Functions:

• Introduced a generic ref function in commercetools/utils.go to simplify pointer creation for any type.

Documentation and Metadata:

• Added a changelog entry (Added-20250711-133538.yaml) documenting the addition of support for the product type attribute level field.