Fix OpenAPI server URLs for Aspire scenarios

[captainsafia]

Description

This PR supports respecting he X-Forwarded-Proto and X-Forwarded-Host headers when generating server URLs in OpenAPI documents. When these headers are present in the request, the OpenAPI document service will use them to generate the correct server URLs instead of using the original host and scheme values derived from the service configuration.

This is particularly useful in environments where the API is behind a proxy, load balancer, or gateway, allowing the generated OpenAPI document to correctly reference the public-facing URL rather than the internal service URL.

Fixes #57332

Customer Impact

Without this change, documents served behind reverse proxies or forwarded endpoints do not reflect the correct service URl, particularly impact for the ASP.NET Core + Aspire scenario. While the issue is easy to workaround, we want a smoother experience with Aspire out-of-the-box.

Regression?

• Yes
• No

Risk

• High
• Medium
• Low

Low-risk, becase change as it only affects the generation of server URLs in OpenAPI documents and does not impact the actual API functionality.

Verification

• Manual (required)
• Automated

Packaging changes reviewed?

• Yes
• No
• N/A

[Copilot]

PR Overview

This PR fixes the generation of OpenAPI server URLs in proxy scenarios by properly using X-Forwarded-Proto and X-Forwarded-Host headers to compute the externally accessible URLs.

• Adds new tests to validate behavior with different forwarded header values.
• Updates the OpenApiDocumentService API to accept an optional HttpRequest parameter and adjust server URL construction accordingly.
• Modifies the endpoint extension to propagate the HttpRequest to the document service.

Reviewed Changes

File	Description
src/OpenApi/test/Microsoft.AspNetCore.OpenApi.Tests/Services/OpenApiDocumentService/OpenApiDocumentServiceTests.Servers.cs	Introduces tests validating the use of forwarded headers and expected URL generation.
src/OpenApi/src/Services/OpenApiDocumentService.cs	Updates method signatures and logic to use the optional HttpRequest for URL generation.
src/OpenApi/test/Microsoft.AspNetCore.OpenApi.Tests/Services/OpenApiDocumentServiceTestsBase.cs	Updates verification calls to pass null for the httpRequest parameter where not applicable.
src/OpenApi/src/Extensions/OpenApiEndpointRouteBuilderExtensions.cs	Adjusts method calls to pass the HttpRequest in order to leverage the new URL generation logic.

Copilot reviewed 4 out of 4 changed files in this pull request and generated 2 comments.

[wtgodbe]

Approved over email