feat: consume transactional email notifications

Add contract validation, SMTP delivery results, terminal failure context, neutral development seeding, and local Docker setup.

Ref: IT-1033

HrynCo.NotificationService.Worker/Properties/AssemblyInfo.cs

@@ -0,0 +1,3 @@
+using System.Runtime.CompilerServices;
+
+[assembly: InternalsVisibleTo("HrynCo.NotificationService.Services.Tests")]

HrynCo.NotificationService.Worker/SendEmailConsumer.cs

@@ -1,14 +1,17 @@
 namespace HrynCo.NotificationService.Worker;
 
 using HrynCo.NotificationService.Contracts.Messages;
-using Hrynco.RabbitMq;
-using Microsoft.Extensions.DependencyInjection;
-using Microsoft.Extensions.Options;
 using HrynCo.NotificationService.Worker.Services.EmailProcessing;
+using Hrynco.RabbitMq;
+using Microsoft.Extensions.Options;
 
 public sealed class SendEmailConsumer : RabbitMqConsumerBase<SendEmailMessage, SendEmailMessageData>
 {
+    internal const string IncomingQueue = "notification.send-email";
+    internal const string SupportedMessageType = "Notification.SendEmail.v1";
+
     private readonly IServiceScopeFactory _scopeFactory;
+    private readonly ILogger<SendEmailConsumer> _logger;
 
     public SendEmailConsumer(
         IOptionsMonitor<RabbitMqSettings> options,
@@ -17,16 +20,51 @@ public sealed class SendEmailConsumer : RabbitMqConsumerBase<SendEmailMessage, S
         : base(options, logger)
     {
         _scopeFactory = scopeFactory;
+        _logger = logger;
     }
 
-    private const string IncomingQueue = "notification.send-email";
-
     protected override string QueueName => IncomingQueue;
 
-    protected override async Task HandleMessageAsync(SendEmailMessage message, CancellationToken cancellationToken)
+    protected override bool TryValidateMessage(
+        SendEmailMessage message,
+        RabbitMqMessageContext context,
+        out string? validationError)
     {
-        using var scope = _scopeFactory.CreateScope();
-        var service = scope.ServiceProvider.GetRequiredService<ISendEmailService>();
+        validationError = SendEmailDeliveryValidator.GetValidationError(
+            message,
+            context,
+            SupportedMessageType);
+        return validationError is null;
+    }
+
+    protected override async Task HandleMessageAsync(
+        SendEmailMessage message,
+        RabbitMqMessageContext context,
+        CancellationToken cancellationToken)
+    {
+        string payloadCorrelationId = message.CorrelationContext.CorrelationId;
+        if (!string.IsNullOrWhiteSpace(context.CorrelationId) &&
+            !string.Equals(context.CorrelationId, payloadCorrelationId, StringComparison.Ordinal))
+        {
+            _logger.LogWarning(
+                "Broker and payload correlation IDs differ; payload correlation ID will be used");
+        }
+
+        await using AsyncServiceScope scope = _scopeFactory.CreateAsyncScope();
+        ISendEmailService service = scope.ServiceProvider.GetRequiredService<ISendEmailService>();
         await service.ProcessAsync(message, cancellationToken);
     }
+
+    protected override async Task HandleMessageRetriesExhaustedAsync(
+        SendEmailMessage message,
+        RabbitMqMessageContext context,
+        Exception exception,
+        CancellationToken cancellationToken)
+    {
+        string deliveryError = NotificationDeliveryErrorFormatter.Format(exception);
+        await using AsyncServiceScope scope = _scopeFactory.CreateAsyncScope();
+        INotificationResultPublisher resultPublisher =
+            scope.ServiceProvider.GetRequiredService<INotificationResultPublisher>();
+        await resultPublisher.PublishAsync(message, deliveryError, cancellationToken);
+    }
 }

HrynCo.NotificationService.Worker/SendEmailDeliveryValidator.cs

@@ -0,0 +1,30 @@
+namespace HrynCo.NotificationService.Worker;
+
+using HrynCo.NotificationService.Contracts.Messages;
+using HrynCo.NotificationService.Worker.Services.EmailProcessing;
+using Hrynco.RabbitMq;
+
+internal static class SendEmailDeliveryValidator
+{
+    public static string? GetValidationError(
+        SendEmailMessage message,
+        RabbitMqMessageContext context,
+        string supportedMessageType)
+    {
+        if (string.IsNullOrWhiteSpace(context.MessageId))
+            return "AMQP MessageId is required.";
+
+        if (!string.Equals(context.MessageType, supportedMessageType, StringComparison.Ordinal))
+            return $"Unsupported AMQP message type '{context.MessageType ?? "<missing>"}'.";
+
+        try
+        {
+            SendEmailMessageValidator.Validate(message);
+            return null;
+        }
+        catch (InvalidDataException exception)
+        {
+            return exception.Message;
+        }
+    }
+}