fix(auth): trace a reset email the provider rejects as an error

A send that the mail provider did not accept finished its background
transaction as ok, so rejected reset emails looked delivered in tracing.
It now finishes as an error with a fixed message that names no recipient.

Api.SeaHavenIndustries.Tests/PasswordResetEmailSenderTracingTests.cs

@@ -0,0 +1,55 @@
+using Api.SeaHavenIndustries.HostedServices;
+using Microsoft.Extensions.DependencyInjection;
+using Microsoft.Extensions.Logging.Abstractions;
+using Moq;
+using Sentry;
+using SeaHaven.Services.Interfaces;
+using Xunit;
+
+namespace Api.SeaHavenIndustries.Tests;
+
+public class PasswordResetEmailSenderTracingTests
+{
+    [Theory]
+    [InlineData(true)]
+    [InlineData(false)]
+    public async Task Each_send_finishes_its_transaction_as_ok_only_when_the_provider_accepts_it(bool accepted)
+    {
+        var transaction = new Mock<ITransactionTracer>();
+        var hub = new Mock<IHub>();
+        hub.Setup(h => h.PushScope()).Returns(Mock.Of<IDisposable>());
+        hub.Setup(h => h.StartTransaction(It.IsAny<ITransactionContext>(), It.IsAny<IReadOnlyDictionary<string, object?>>()))
+            .Returns(transaction.Object);
+
+        var sender = new Mock<IEmailSender>();
+        sender.Setup(s => s.SendEmailAsync(It.IsAny<string>(), It.IsAny<string>(), It.IsAny<string>())).ReturnsAsync(accepted);
+        var services = new ServiceCollection().AddSingleton(sender.Object).BuildServiceProvider();
+        var channel = new PasswordResetEmailChannel(NullLogger<PasswordResetEmailChannel>.Instance);
+        var worker = new PasswordResetEmailSenderHostedService(
+            channel,
+            services.GetRequiredService<IServiceScopeFactory>(),
+            NullLogger<PasswordResetEmailSenderHostedService>.Instance,
+            hub.Object);
+
+        await worker.StartAsync(CancellationToken.None);
+        Assert.True(channel.TryEnqueue("user@example.com", "subject", "Your code is 123456"));
+        var deadline = DateTime.UtcNow.AddSeconds(10);
+        while (channel.Pending > 0 && DateTime.UtcNow < deadline)
+            await Task.Delay(10);
+        await worker.StopAsync(CancellationToken.None);
+
+        Assert.Equal(0, channel.Pending);
+        if (accepted)
+        {
+            transaction.Verify(t => t.Finish(SpanStatus.Ok), Times.Once);
+            transaction.Verify(t => t.Finish(It.IsAny<Exception>(), It.IsAny<SpanStatus>()), Times.Never);
+        }
+        else
+        {
+            transaction.Verify(t => t.Finish(SpanStatus.Ok), Times.Never);
+            transaction.Verify(t => t.Finish(
+                It.Is<Exception>(ex => !ex.Message.Contains("user@example.com") && !ex.Message.Contains("123456")),
+                SpanStatus.InternalError), Times.Once);
+        }
+    }
+}

Api.SeaHavenIndustries/HostedServices/PasswordResetEmailDelivery.cs

@@ -91,8 +91,10 @@ namespace Api.SeaHavenIndustries.HostedServices
                     $"{nameof(PasswordResetEmailSenderHostedService)}.{nameof(SendAsync)}");
                 try
                 {
-                    await SendAsync(email);
+                    if (await SendAsync(email))
                         transaction.FinishOk();
+                    else
+                        transaction.FinishError(new InvalidOperationException("The mail provider did not accept the password reset email."));
                 }
                 catch (OperationCanceledException) when (stoppingToken.IsCancellationRequested)
                 {
@@ -112,12 +114,16 @@ namespace Api.SeaHavenIndustries.HostedServices
             }
         }
 
-        private async Task SendAsync(PasswordResetEmail email)
+        /// <summary>True when the mail provider accepted the email.</summary>
+        private async Task<bool> SendAsync(PasswordResetEmail email)
         {
             await using var scope = _scopeFactory.CreateAsyncScope();
             var sender = scope.ServiceProvider.GetRequiredService<IEmailSender>();
-            if (!await sender.SendEmailAsync(email.EmailTo, email.Subject, email.Body))
+            if (await sender.SendEmailAsync(email.EmailTo, email.Subject, email.Body))
+                return true;
+
             _logger.LogWarning("Password reset email was not accepted by the mail provider.");
+            return false;
         }
     }
 }