[What's New Analysis] Document external service modeling

Summary

Aspire 9.4 introduced AddExternalService() for modeling third-party APIs and existing infrastructure not managed by Aspire. This is only in what's-new.

What's Missing

Core API

var builder = DistributedApplication.CreateBuilder(args);

// Reference an external service by URL
var externalApi = builder.AddExternalService("external-api", "https://api.company.com");

// Or use a parameter for dynamic configuration
var apiUrl = builder.AddParameter("api-url");
var externalDb = builder.AddExternalService("external-db", apiUrl)
    .WithHttpHealthCheck("/health");

var myService = builder.AddProject<Projects.MyService>("my-service")
    .WithReference(externalApi)
    .WithReference(externalDb);

Features

• External services appear in the Aspire dashboard with health status
• Can be referenced like any other resource
• Support same configuration patterns as internal resources
• Health checks via WithHttpHealthCheck()

Suggested Content

1. When to use external services - third-party APIs, legacy systems, shared infrastructure
2. API reference - AddExternalService overloads
3. Health checks - WithHttpHealthCheck configuration
4. Dashboard integration - how external services appear
5. Examples - external database, payment API, auth service

Why It Matters

Most real-world apps integrate with external services. Users need to model these dependencies for accurate architecture visualization.