Fix case-insensitive group name matching in OpenAPI document filtering

src/OpenApi/src/Services/OpenApiOptions.cs

@@ -29,7 +29,7 @@ public sealed class OpenApiOptions
     /// </summary>
     public OpenApiOptions()
     {
-        ShouldInclude = (description) => description.GroupName == null || description.GroupName == DocumentName;
+        ShouldInclude = (description) => description.GroupName == null || string.Equals(description.GroupName, DocumentName, StringComparison.OrdinalIgnoreCase);
     }
 
     /// <summary>

src/OpenApi/test/Microsoft.AspNetCore.OpenApi.Tests/Services/OpenApiDocumentService/OpenApiDocumentServiceTests.Paths.cs

@@ -3,6 +3,7 @@
 
 using System.Net.Http;
 using Microsoft.AspNetCore.Builder;
+using Microsoft.AspNetCore.OpenApi;
 using Microsoft.AspNetCore.Routing;
 
 public partial class OpenApiDocumentServiceTests : OpenApiDocumentServiceTestBase
@@ -67,6 +68,31 @@ await VerifyOpenApiDocument(builder, document =>
         });
     }
 
+    [Fact]
+    public async Task GetOpenApiPaths_RespectsShouldInclude_CaseInsensitive()
+    {
+        // Arrange
+        var builder = CreateBuilder();
+        var openApiOptions = new OpenApiOptions { DocumentName = "firstgroup" };
+
+        // Act
+        builder.MapGet("/api/todos", () => { }).WithMetadata(new EndpointGroupNameAttribute("FirstGroup"));
+        builder.MapGet("/api/users", () => { }).WithMetadata(new EndpointGroupNameAttribute("SecondGroup"));
+
+        // Assert -- The default `ShouldInclude` implementation should include endpoints that
+        // match the document name case-insensitively. The document name is "firstgroup" (lowercase)
+        // but the endpoint group name is "FirstGroup" (mixed case), and it should still match.
+        await VerifyOpenApiDocument(builder, openApiOptions, document =>
+        {
+            Assert.Collection(document.Paths.OrderBy(p => p.Key),
+                path =>
+                {
+                    Assert.Equal("/api/todos", path.Key);
+                }
+            );
+        });
+    }
+
     [Fact]
     public async Task GetOpenApiPaths_RespectsSamePaths()
     {