Add ProducesResponseType Description documentation

[sander1095]

The "What's new in .NET 10" release notes mention the new Description property I added, but the .NET 10 OpenAPI docs do not.
This commit adds consistency.

I've added examples for ProducesResponseType and ProducesDefaultResponseType to Minimal API and Controller docs. I know a team member doesn't like ProducesDefault (@mikekistler, dotnet/aspnetcore#58719 (comment) ).

I also know that another team member (@captainsafia , dotnet/aspnetcore#58724 (comment)) would prefer developers to use the endpoint-specific OpenAPI transformers (Which will be released in a future preview) instead of setting the Description for Minimal API's, as they are more extensible.

Therefore, I'd like to discuss the following:

• Should we choose to NOT showcase code examples for ProducesDefault? This way, we make it clear that it IS possible by mentioning it's existance, but also "discourage" developers from using it by not showing any explicit code examples.
• I believe it's important to update both the Controllers and Minimal API docs and highlight this new Description property. However, when Support registering OpenApiOperationTransformer via extension method for Minimal APIs aspnetcore#59180 lands in a future preview, I'd propose we update this page and mention that THAT approach is preferred over the Description property in Minimal API scenario's.

Fixes #33974
Fixes #35016

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Internal previews

📄 File	🔗 Preview link
aspnetcore/fundamentals/openapi/include-metadata.md	aspnetcore/fundamentals/openapi/include-metadata

[sander1095]

I've had issues with the moniker for .NET 10 in a previous PR. I see the build fails here, and I assume it is for the same reason, as I can't get any useful info about the error in the failed pipeline. I might need some help with that :)

[sander1095]

Sidenote: .NET 10 Preview 1's ProducesResponseType now has a Description attribute, but I do not see this in the docs.

When I click on the Version dropdown and select ASP.NET Core 10, it quickly shows "ASP.NET Core in .NET 10.0 Preview` and switches back to NET 9.0. Have the docs not been updated yet?

[guardrex]

Hello @sander1095 ... The build warnings this morning are appearing on all of our PRs and are unrelated to what you're submitting. A member of our team will file an internal bug report on them.

[guardrex]

@captainsafia ... No giant rush, just making sure that you saw the ping on this one.

[guardrex]

I added a very quick pass to update code spacing and a few other NITs 😈.

[guardrex]

Looks like we'll still need a What's New article entry for this in ......

https://github.com/dotnet/AspNetCore.Docs/blob/main/aspnetcore/release-notes/aspnetcore-10/includes/openApi.md

Nevermind! ... I see it now. It's in a different file ...

https://github.com/dotnet/AspNetCore.Docs/blob/main/aspnetcore/release-notes/aspnetcore-10/includes/responseDescProducesResponseType.md