Add database seeder with sample data and test guide

src/Hospitality.Backend/Program.cs

@@ -22,6 +22,14 @@ builder.Services.AddScoped<ITransactionService, TransactionService>();
 
 var app = builder.Build();
 
+// Seed database with sample data
+using (var scope = app.Services.CreateScope())
+{
+    var context = scope.ServiceProvider.GetRequiredService<HospitalityDbContext>();
+    await Hospitality.Backend.Data.DbSeeder.SeedAsync(context);
+}
+
+
 // Configure the HTTP request pipeline.
 if (app.Environment.IsDevelopment())
 {