Deleted client/credential.go and moved the Credentials struct to the api package for better modularity. Enhanced type safety in api by checking type assertions and added detailed comments in model structs.
Streamlined API client initialization within the NewApi function by directly invoking the client creation. Additionally, removed custom type declarations and constants in model/product.go, replacing them with simpler string types to reduce complexity.
This commit introduces new API and client modules that provide functionality for managing categories and products. It includes the creation of `.gitignore`, necessary data models, API endpoints, and client authentication using go-resty. This forms the foundation for further enhancements to the category and product management features.