Amortise Content-Type arrays (#56525)

- Amortise arrays used for `TypedResults`' metadata.
- Use `ProducesResponseTypeMetadata.CreateUnvalidated` to bypass `Content-Type` validation for static values.
- Add and use constant for `application/octet-stream`.

Author: martincostello

src/Http/Http.Abstractions/src/Microsoft.AspNetCore.Http.Abstractions.csproj

@@ -37,6 +37,7 @@ Microsoft.AspNetCore.Http.HttpResponse</Description>
   <ItemGroup>
     <InternalsVisibleTo Include="Microsoft.AspNetCore.Http.Abstractions.Microbenchmarks" />
     <InternalsVisibleTo Include="Microsoft.AspNetCore.Http.Extensions" />
+    <InternalsVisibleTo Include="Microsoft.AspNetCore.Http.Results" />
   </ItemGroup>
 
   <ItemGroup>

src/Http/Http.Results/src/AcceptedAtRouteOfT.cs

@@ -122,6 +122,6 @@ static void IEndpointMetadataProvider.PopulateMetadata(MethodInfo method, Endpoi
         ArgumentNullException.ThrowIfNull(method);
         ArgumentNullException.ThrowIfNull(builder);
 
-        builder.Metadata.Add(new ProducesResponseTypeMetadata(StatusCodes.Status202Accepted, typeof(TValue), new[] { "application/json" }));
+        builder.Metadata.Add(ProducesResponseTypeMetadata.CreateUnvalidated(typeof(TValue), StatusCodes.Status202Accepted, HttpResultsHelper.ApplicationJsonContentTypes));
     }
 }

src/Http/Http.Results/src/AcceptedOfT.cs

@@ -100,6 +100,6 @@ static void IEndpointMetadataProvider.PopulateMetadata(MethodInfo method, Endpoi
         ArgumentNullException.ThrowIfNull(method);
         ArgumentNullException.ThrowIfNull(builder);
 
-        builder.Metadata.Add(new ProducesResponseTypeMetadata(StatusCodes.Status202Accepted, typeof(TValue), new[] { "application/json" }));
+        builder.Metadata.Add(ProducesResponseTypeMetadata.CreateUnvalidated(typeof(TValue), StatusCodes.Status202Accepted, HttpResultsHelper.ApplicationJsonContentTypes));
     }
 }

src/Http/Http.Results/src/BadRequestOfT.cs

@@ -65,6 +65,6 @@ static void IEndpointMetadataProvider.PopulateMetadata(MethodInfo method, Endpoi
         ArgumentNullException.ThrowIfNull(method);
         ArgumentNullException.ThrowIfNull(builder);
 
-        builder.Metadata.Add(new ProducesResponseTypeMetadata(StatusCodes.Status400BadRequest, typeof(TValue), new[] { "application/json" }));
+        builder.Metadata.Add(ProducesResponseTypeMetadata.CreateUnvalidated(typeof(TValue), StatusCodes.Status400BadRequest, HttpResultsHelper.ApplicationJsonContentTypes));
     }
 }

src/Http/Http.Results/src/ConflictOfT.cs

@@ -65,6 +65,6 @@ static void IEndpointMetadataProvider.PopulateMetadata(MethodInfo method, Endpoi
         ArgumentNullException.ThrowIfNull(method);
         ArgumentNullException.ThrowIfNull(builder);
 
-        builder.Metadata.Add(new ProducesResponseTypeMetadata(StatusCodes.Status409Conflict, typeof(TValue), new[] { "application/json" }));
+        builder.Metadata.Add(ProducesResponseTypeMetadata.CreateUnvalidated(typeof(TValue), StatusCodes.Status409Conflict, HttpResultsHelper.ApplicationJsonContentTypes));
     }
 }

src/Http/Http.Results/src/CreatedAtRouteOfT.cs

@@ -125,6 +125,6 @@ static void IEndpointMetadataProvider.PopulateMetadata(MethodInfo method, Endpoi
         ArgumentNullException.ThrowIfNull(method);
         ArgumentNullException.ThrowIfNull(builder);
 
-        builder.Metadata.Add(new ProducesResponseTypeMetadata(StatusCodes.Status201Created, typeof(TValue), new[] { "application/json" }));
+        builder.Metadata.Add(ProducesResponseTypeMetadata.CreateUnvalidated(typeof(TValue), StatusCodes.Status201Created, HttpResultsHelper.ApplicationJsonContentTypes));
     }
 }

src/Http/Http.Results/src/CreatedOfT.cs

@@ -99,6 +99,6 @@ static void IEndpointMetadataProvider.PopulateMetadata(MethodInfo method, Endpoi
         ArgumentNullException.ThrowIfNull(method);
         ArgumentNullException.ThrowIfNull(builder);
 
-        builder.Metadata.Add(new ProducesResponseTypeMetadata(StatusCodes.Status201Created, typeof(TValue), new[] { "application/json" }));
+        builder.Metadata.Add(ProducesResponseTypeMetadata.CreateUnvalidated(typeof(TValue), StatusCodes.Status201Created, HttpResultsHelper.ApplicationJsonContentTypes));
     }
 }

src/Http/Http.Results/src/FileContentHttpResult.cs

@@ -61,7 +61,7 @@ internal FileContentHttpResult(
     {
         FileContents = fileContents;
         FileLength = fileContents.Length;
-        ContentType = contentType ?? "application/octet-stream";
+        ContentType = contentType ?? HttpResultsHelper.BinaryContentType;
         FileDownloadName = fileDownloadName;
         EnableRangeProcessing = enableRangeProcessing;
         LastModified = lastModified;

src/Http/Http.Results/src/FileStreamHttpResult.cs

@@ -67,7 +67,7 @@ internal FileStreamHttpResult(
             FileLength = fileStream.Length;
         }
 
-        ContentType = contentType ?? "application/octet-stream";
+        ContentType = contentType ?? HttpResultsHelper.BinaryContentType;
         FileDownloadName = fileDownloadName;
         EnableRangeProcessing = enableRangeProcessing;
         LastModified = lastModified;

src/Http/Http.Results/src/HttpResultsHelper.cs

@@ -17,7 +17,13 @@ namespace Microsoft.AspNetCore.Http;
 
 internal static partial class HttpResultsHelper
 {
+    internal const string BinaryContentType = "application/octet-stream";
     internal const string DefaultContentType = "text/plain; charset=utf-8";
+    internal const string ProblemDetailsContentType = "application/problem+json";
+
+    internal static IEnumerable<string> ApplicationJsonContentTypes { get; } = ["application/json"];
+    internal static IEnumerable<string> ProblemDetailsContentTypes { get; } = [ProblemDetailsContentType];
+
     private static readonly Encoding DefaultEncoding = Encoding.UTF8;
 
     [UnconditionalSuppressMessage("Trimming", "IL2026:RequiresUnreferencedCode",