feat(storage): add new storage exception and expose code parameter

[jan-tennert]

What kind of change does this PR introduce?

Feature (closes #1372)

This pull request refactors error handling in the Storage module to provide more detailed and structured exceptions for storage API errors. Instead of using generic or HTTP-based exceptions, a new StorageRestException is introduced, which includes a service-specific error code for improved error handling and debugging. Imports are cleaned up, and the error response data class is updated to include the new code field.

Error handling improvements:

• Replaced previous exception handling logic in StorageImpl to always throw a new StorageRestException, which provides a more detailed and consistent error structure, including the storage-specific error code.
• Added new StorageRestException class to encapsulate storage-specific error details, including the API error code, message, and HTTP status code.
• Updated StorageErrorResponse data class to include a code field for the service-specific error code from the Storage API.

Codebase cleanup:

• Removed unused exception and HTTP imports from Storage.kt to simplify dependencies.
• Made the statusCode property in RestException open, allowing subclasses like StorageRestException to override it.