Program.cs

using System.Diagnostics.CodeAnalysis;
using System.Text.Json.Serialization;
using JsonApiDotNetCore.Configuration;
using JsonApiDotNetCore.Diagnostics;
using JsonApiDotNetCoreExample.Data;
using JsonApiDotNetCoreExample.Models;
using Microsoft.AspNetCore.Authentication;
using Microsoft.EntityFrameworkCore;
using Microsoft.Extensions.DependencyInjection.Extensions;

[assembly: ExcludeFromCodeCoverage]

WebApplication app = CreateWebApplication(args);

await CreateDatabaseAsync(app.Services);

app.Run();

static WebApplication CreateWebApplication(string[] args)
{
    using ICodeTimerSession codeTimerSession = new DefaultCodeTimerSession();
    CodeTimingSessionManager.Capture(codeTimerSession);

    WebApplicationBuilder builder = WebApplication.CreateBuilder(args);

    // Add services to the container.
    ConfigureServices(builder);

    WebApplication webApplication = builder.Build();

    // Configure the HTTP request pipeline.
    ConfigurePipeline(webApplication);

    if (CodeTimingSessionManager.IsEnabled)
    {
        string timingResults = CodeTimingSessionManager.Current.GetResults();
        webApplication.Logger.LogInformation($"Measurement results for application startup:{Environment.NewLine}{timingResults}");
    }

    return webApplication;
}

static void ConfigureServices(WebApplicationBuilder builder)
{
    using IDisposable _ = CodeTimingSessionManager.Current.Measure("Configure services");

    builder.Services.TryAddSingleton<ISystemClock, SystemClock>();

    builder.Services.AddDbContext<AppDbContext>(options =>
    {
        string connectionString = GetConnectionString(builder.Configuration);

        options.UseNpgsql(connectionString);
#if DEBUG
        options.EnableSensitiveDataLogging();
        options.EnableDetailedErrors();
#endif
    });

    using (CodeTimingSessionManager.Current.Measure("AddJsonApi()"))
    {
        builder.Services.AddJsonApi<AppDbContext>(options =>
        {
            options.Namespace = "api/v1";
            options.UseRelativeLinks = true;
            options.IncludeTotalResourceCount = true;
            options.SerializerOptions.WriteIndented = true;
            options.SerializerOptions.Converters.Add(new JsonStringEnumConverter());
#if DEBUG
            options.IncludeExceptionStackTraceInErrors = true;
            options.IncludeRequestBodyInErrors = true;
#endif
        }, discovery => discovery.AddCurrentAssembly());
    }
}

static string GetConnectionString(IConfiguration configuration)
{
    string postgresPassword = Environment.GetEnvironmentVariable("PGPASSWORD") ?? "postgres";
    return configuration["Data:DefaultConnection"].Replace("###", postgresPassword);
}

static void ConfigurePipeline(WebApplication webApplication)
{
    using IDisposable _ = CodeTimingSessionManager.Current.Measure("Configure pipeline");

    webApplication.UseRouting();

    using (CodeTimingSessionManager.Current.Measure("UseJsonApi()"))
    {
        webApplication.UseJsonApi();
    }

    webApplication.MapControllers();
}

static async Task CreateDatabaseAsync(IServiceProvider serviceProvider)
{
    await using AsyncServiceScope scope = serviceProvider.CreateAsyncScope();

    var dbContext = scope.ServiceProvider.GetRequiredService<AppDbContext>();

    await dbContext.Database.EnsureDeletedAsync();
    await dbContext.Database.EnsureCreatedAsync();

    var postIt = new PostIt
    {
        Id = 835405,
        Actif = true,
        Date = DateTime.UtcNow,
        Message = "ab",
        OtherMessage = "cd",
        RefOperateur = "some-ref"
    };

    dbContext.PostIts.Add(postIt);

    await dbContext.SaveChangesAsync();
}