Correct AddOpenApi() service registration syntax

[wadepickett]

Description

The documentation incorrectly showed builder.AddOpenApi() when AddOpenApi() is an extension method on IServiceCollection, not WebApplicationBuilder.

Changes
Lines 135-136: Updated service registration to use builder.Services.AddOpenApi() instead of builder.AddOpenApi()
Metadata: Added ai-usage: ai-assisted and updated ms.date per repository guidelines
Example
Before:

builder.AddOpenApi(); // Adds "v1" by default
builder.AddOpenApi("v2");
builder.Services.AddScoped();
After:

builder.Services.AddOpenApi(); // Adds "v1" by default
builder.Services.AddOpenApi("v2");
builder.Services.AddScoped();
This aligns with standard ASP.NET Core DI patterns and the actual API surface.

Page URL

https://learn.microsoft.com/en-us/aspnet/core/fundamentals/openapi/using-openapi-documents?view=aspnetcore-10.0

Content source URL

https://github.com/dotnet/AspNetCore.Docs/blob/main/aspnetcore/fundamentals/openapi/using-openapi-documents.md

Document ID

472b10ab-681b-f631-040d-025ef0a02329

Platform Id

c973de58-a013-4aa0-ccef-0bd78e4749db

Article author

@captainsafia

Metadata

• ID: 472b10ab-681b-f631-040d-025ef0a02329
• PlatformId: c973de58-a013-4aa0-ccef-0bd78e4749db
• Service: aspnet-core
• Sub-service: fundamentals

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