Initial exercise setup.

Additions

* Instructions for manually starting the database.
* Each phase now has a success criteria with how to verify.
* Troubleshooting section for working with the Docker DB container.
* All phases of the exercise are described in README.md (with as little advanced hints as possible).
* DFD to illustrate phase 1
* Debugging starts the database container and applies schema migrations (no setup required).
* Launch settings for VS Code, VS 2022 and Rider (IntelliJ IDEA).
* Swagger UI is available at <http://localhost:8080/swagger/index.html> for testing.

service/Program.cs

@@ -0,0 +1,46 @@
+using System;
+using System.Net.Http;
+using System.Threading;
+using System.Threading.Tasks;
+using Microsoft.AspNetCore.Builder;
+using Microsoft.AspNetCore.Http;
+using Microsoft.EntityFrameworkCore;
+using Microsoft.Extensions.Configuration;
+using Microsoft.Extensions.DependencyInjection;
+using Polly.Simmy;
+
+using service;
+
+var builder = WebApplication.CreateBuilder(args);
+
+// Add services to the container.
+var services = builder.Services;
+services.AddRequestTimeouts();
+// Learn more about configuring Swagger/OpenAPI at https://aka.ms/aspnetcore/swashbuckle
+services.AddEndpointsApiExplorer();
+services.AddSwaggerGen();
+services.AddDbContext<AppDbContext>(optionsBuilder =>
+{
+    // Configure the database connection string.
+    var connectionString = builder.Configuration.GetValue<string>("PostgresConnection");
+    Console.WriteLine($"Connecting to PostgreSQL database with connection string: {connectionString}");
+    optionsBuilder.UseNpgsql(connectionString);
+});
+var httpClientBuilder = services.AddHttpClient<JsonPlaceholderClient>();
+
+var app = builder.Build();
+app.UseSwagger();
+app.UseSwaggerUI(); // Swagger UI is available at http://localhost:8080/swagger/index.html
+app.UseRequestTimeouts();
+
+app.MapGet("/posts/{id}", async (AppDbContext dbContext, JsonPlaceholderClient client, int id) =>
+{
+    // TODO: (Phase 1) Implement the logic to retrieve a post by ID and store it in the database.
+    // Consider some minimal error handling in case the post is not found (e.g. Id > 100).
+    return Results.Ok();
+})
+.WithRequestTimeout(TimeSpan.FromSeconds(29))
+.WithName("GetPostById")
+.WithOpenApi();
+
+app.Run();