Implement .NET Aspire orchestration in Chapter 3 with RabbitMQ and PostgreSQL

[Copilot]

📋 Description

Adds .NET Aspire as an alternative orchestration method for Chapter 3's microservices architecture. Provides service orchestration, built-in observability, and automatic dependency management while maintaining full backward compatibility with existing docker-compose setup.

New Projects

• Fitnet.AppHost: Orchestrates PostgreSQL, RabbitMQ, Fitnet monolith, and Contracts microservice
• Fitnet.ServiceDefaults: Shared library for OpenTelemetry, service discovery, health checks, and HTTP resilience

Connection String Pattern

All database and messaging modules now prioritize Aspire connection strings with fallback to legacy configuration:

// EventBusModule.cs - RabbitMQ
var connectionString = configuration.GetConnectionString("rabbitmq");
if (!string.IsNullOrEmpty(connectionString))
{
    factoryConfigurator.Host(new Uri(connectionString));
}
else
{
    // Fallback to EventBusOptions
    factoryConfigurator.Host(options.Value.Uri, ...);
}

// DatabaseModule.cs - PostgreSQL
var connectionString = configuration.GetConnectionString("fitnet");
if (string.IsNullOrEmpty(connectionString))
{
    connectionString = databaseOptions.Value.ConnectionString;
}
options.UseNpgsql(connectionString);

Service Integration

// Program.cs
builder.AddServiceDefaults();  // OpenTelemetry, service discovery, resilience
app.MapDefaultEndpoints();     // /health and /alive endpoints

AppHost Configuration

var postgres = builder.AddPostgres("postgres")
    .WithImage("postgres").WithImageTag("14.3")
    .WithHealthCheck();

var rabbitmq = builder.AddRabbitMQ("rabbitmq")
    .WithManagementPlugin()
    .WithHealthCheck();

builder.AddProject<Projects.Fitnet>("fitnet-modular-monolith")
    .WithReference(postgres.AddDatabase("fitnet"))
    .WithReference(rabbitmq);

Usage

cd Fitnet.AppHost && dotnet run

Aspire Dashboard provides unified view of services, traces, metrics, and logs. Applications remain accessible at ports 8080 (Fitnet) and 8081 (Contracts).

📦 PR Includes

• Feature added 🆕
• Bug fix 🐛
• Code refactor 🔄
• Documentation update 📚
• Tests added/updated 🧪
• Other: (describe)

🚫 PR Does Not Include

• Breaking changes ❌
• Major architectural changes 🏗️
• Unrelated features/tasks 🚫

💡 Additional Notes

Files Modified: 10 (connection string handling in DatabaseModule/EventBusModule across all modules, Program.cs integration)
Files Created: 6 (AppHost, ServiceDefaults, documentation)
Stats: +621/-16 lines

Backward compatible: docker-compose.yml workflow unchanged, services run with or without Aspire. No changes to business logic or existing tests.

See Docs/ASPIRE_IMPLEMENTATION.md for architecture details and implementation patterns.

Original prompt

Aspire in chapter 3 implement rabbit mq in aspire

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