First commit that builds.

code/MessengerBroker/Program.cs

@@ -0,0 +1,102 @@
+using MessengerBroker.Handlers;
+using MessengerBroker.Model.Http;
+using System.Runtime.CompilerServices;
+
+namespace MessengerBroker
+{
+    public class Program
+    {
+        public static void Main(string[] args)
+        {
+            var settings = (Settings)null;
+            var builder = WebApplication.CreateBuilder(args);
+            var app = builder.Build();
+
+            app.MapGet("/users", async (HttpContext httpContext) =>
+            {
+                var authHandler = app.Services.GetService<AuthHandler>();
+                var brokerId = authHandler.Auth(httpContext);
+
+                if(brokerId == null)
+                {
+                    return Results.Unauthorized();
+                }
+
+                var dataHandler = app.Services.GetService<DataHandler>();
+                var usersAndRoutes = await dataHandler.GetLocalUsersAndRoutes();
+
+                var response = new Users.UsersResponse
+                {
+                    Users = usersAndRoutes.Item1.Select(x => new Users.UsersResponse.User
+                    {
+                        Id = x.Id,
+                        Name = x.Name,
+                        ApiKey = x.ApiKey,
+                        CanReceive = x.CanReceive,
+                        CanSend = x.CanSend,
+                        IsEnabled = x.IsEnabled,
+                    }).ToArray(),
+                    UserRoutes = usersAndRoutes.Item2.Select(x => new Users.UsersResponse.UserRoute
+                    {
+                        Id = x.Id,
+                        FromId = x.From.Id,
+                        ToId = x.To.Id
+                    }).ToArray()
+                };
+
+                return Results.Json(response);
+            });
+
+            app.MapGet("/sync", async (HttpContext httpContext, [AsParameters] Sync.SyncRequest request) =>
+            {
+                var authHandler = app.Services.GetService<AuthHandler>();
+                var brokerId = authHandler.Auth(httpContext);
+
+                if(brokerId == null)
+                {
+                    return Results.Unauthorized();
+                }
+                else if(request.BrokerId != brokerId && request.BrokerId != settings.BrokerId)
+                {
+                    return Results.Unauthorized();
+                }
+
+                var dataHandler = app.Services.GetService<DataHandler>();
+                var messages = await dataHandler.GetMessages(request.BrokerId, request.SinceUtc);
+
+                var response = new Sync.SyncResponse
+                {
+                    Messages = messages.Select(x => new Sync.SyncResponse.Message
+                    {
+                        Id = x.Id,
+                        CreatedUtc = x.CreatedUtc,
+                        From = x.From.Id,
+                        To = x.To.Id,
+                        IsAcknowledged = x.IsAcknowledged,
+                        IsDelivered = x.IsDelivered,
+                        Payload = x.Payload,
+                        PayloadId = x.PayloadId,
+                        PayloadLifespanInSeconds = x.PayloadLifespanInSeconds,
+                        PayloadTimestamp = x.PayloadTimestamp,
+                        PayloadType = x.PayloadType
+                    }).ToArray()
+                };
+
+                return Results.Json(response);
+            });
+
+            _ = Task.Run(async () =>
+            {
+                var cts = new CancellationTokenSource();
+                var handler = app.Services.GetService<MasterHandler>();
+
+                foreach(var master in settings.Masters)
+                {
+                    _ = handler.BeginSyncingWithMaster(master, cts.Token);
+                }
+            });
+
+            app.Run();
+        }
+    }
+}