Produces generic variants of `ProducesProblem` extension methods

[mikekistler]

Background and Motivation

The ProducesProblem extension method can be specified on a RouteHandlerBuilder to specify that the route handler may return a ProblemDetails response. But unlike similar extension methods to add endpoint metadata, e.g. WithDescription or WithTags, the ProducesProblem extension method is not supported on RouteGroupBuilder. Since nearly every operation can fail in some way or other, it seems desirable to be able to easily mark all route handlers in a group as potentially returning ProblemDetails, and doing this with the ProducesProblem method on the RouteGroupBuilder is the most natural way to do this.

Proposed API

// Assembly: Microsoft.AspNetCore.Routing

namespace Microsoft.AspNetCore.Http;

public static class OpenApiRouteHandlerBuilderExtensions
{
+	public static TBuilder ProducesProblem<TBuilder>(this TBuilder builder, int statusCode, string? contentType = null) where TBuilder : IEndpointConventionBuilder { }
+	public static ProducesValidationProblem<TBuilder>(this TBuilder builder, int statusCode = StatusCodes.Status400BadRequest, string? contentType = null) where TBuilder : IEndpointConventionBuilder { }
}

Usage Examples

var app = WebApplication.Create();

var todos = app.MapGroup("/todos")
	.ProducesProblem(statusCode: 500, "application/json+problem");

[dotnet-policy-service]

Thank you for submitting this for API review. This will be reviewed by @dotnet/aspnet-api-review at the next meeting of the ASP.NET Core API Review group. Please ensure you take a look at the API review process documentation and ensure that:

• The PR contains changes to the reference-assembly that describe the API change. Or, you have included a snippet of reference-assembly-style code that illustrates the API change.
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• Someone is assigned to "champion" this change in the meeting, and they understand the impact and design of the change.

[amcasey]

[API Review]

No objections in principle.

Some notes from last time:

Remove the MapGroup-supporting TBuilder overloads for Produces/ProducesProblem/ProducesValidationProblem/Accepts because people don’t need them on groups.
we can always add the Produces/ProducesProblem/ProducesValidationProblem/Accepts overloads

We now think our previous decision may have been over-cautious.

We still don't have reasons (other than consistency) to update Produces and Accepts.

PR Approved!

// Assembly: Microsoft.AspNetCore.Routing

namespace Microsoft.AspNetCore.Http;

public static class OpenApiRouteHandlerBuilderExtensions
{
+	public static TBuilder ProducesProblem<TBuilder>(this TBuilder builder, int statusCode, string? contentType = null) where TBuilder : IEndpointConventionBuilder { }
+	public static TBuilder ProducesValidationProblem<TBuilder>(this TBuilder builder, int statusCode = StatusCodes.Status400BadRequest, string? contentType = null) where TBuilder : IEndpointConventionBuilder { }
}