Centralize Input/Output and Data Class Logic in Metadata

[Cafeine42]

Currently, across the codebase (e.g., in ObjectMapperProvider, SerializerContextBuilder, OpenApiFactory), we frequently encounter the pattern of checking for a custom input/output class and falling back to the resource class if not defined:

$class = $operation->getInput()['class'] ?? $operation->getClass();
// or
$class = $operation->getOutput()['class'] ?? $operation->getClass();

To simplify the codebase and avoid repetitive logic, I propose introducing helper methods directly in the Metadata (and thus Operation and ApiResource) classes to handle these fallbacks.

Proposed Changes

The idea is to add the following methods:

1. getInputClass(): ?string: Returns the custom input class if defined, otherwise falls back to getClass().
2. getOutputClass(): ?string: Returns the custom output class if defined, otherwise falls back to getClass().
3. getDataClass(): ?string: (Optional/For discussion) A method to handle the mapped entity class with a similar fallback mechanism, specifically useful when working with DTOs and Data Mappers.

Benefits

• Dry Code: Centralizes the logic in one place.
• Simplification: Reduces boilerplate in providers, processors, and factories.
• Consistency: Ensures the fallback logic is applied identically everywhere.

Considerations

This changes metadata handling significantly. Cleaner API, but assess whether it requires a major (breaking) release or can remain optional.