Add default implementation to OpenAPI's new Description property to prevent a breaking change

[sander1095]

Add default implementation to OpenAPI's new Description property to prevent a breaking change

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This PR adds a default implementation to IProducesResponseTypeMetadata.Description and IApiResponseMetadataProvider.Description to prevent breaking changes.

Description

In #58193 I added a Description property to IProducesResponseType, IApiResponseMetadataProvider, attributes and some other spots to allow developers to easily set response descriptions.

The linked issue tries to cast their own class implementation to IProducesResponseType. Because they don't have Description, an exception is thrown.

This issue is fixed by adding a default implementation of this property.

Fixes #59804

[sander1095]

@captainsafia I just created this quick PR with the desired change you mentioned in the issue.

I want to double check something. The original PR (#58193) adds the property description to multiple places, both classes (and attributes) and an interface (src/Mvc/Mvc.Core/src/ApiExplorer/IApiResponseMetadataProvider.cs).

Would you like me to add a default implementation in more places to avoid this issue to from showing up again in the future? If so, can you provide some direction for which classes this is desired?

If desired, I could also proceed by adding some unit tests that cast the interface the same way the issue does to prevent regression, but I am not sure if this is too specific as we simply missed this in API review.

[sander1095]

From a chat with Safia, a TODO for me:

As far as testing for this, maybe a quick sanity check to see if an implementation of the interface without the property will work fine

Just to be safe we should do a default implementation on all the interfaces that implement it.