Add RabbitMQ integration tests and URL parsing logic

Enhanced test coverage for RabbitMQ integration by adding:
- New package references for dependency injection, logging, and RabbitMQ.
- `EmailSenderCollection` and `EmailSenderFixture` for managing static client lifecycle in integration tests.
- Integration tests for `EmailSender` and `OutgoingEmailPublisher` to verify connection management, message publishing, and serialization.
- `EmailSenderUrlOverloadTests` to validate URL-based connection overload behavior.
- `RabbitMqTestConfig` for centralized RabbitMQ test configuration.
- Unit tests for URL parsing logic in `EmailSenderUrlParsingTests`.

These changes improve reliability, maintainability, and test coverage for the messaging service.

tests/DigitalData.MessagingService.Tests/Integration/EmailSenderTests.cs

@@ -0,0 +1,110 @@
+using DigitalData.MessagingService.Client.DependencyInjection;
+using DigitalData.MessagingService.Publisher.Abstraction;
+
+namespace DigitalData.MessagingService.Tests.Integration;
+
+/// <summary>
+/// xUnit collection that serializes all <see cref="EmailSenderTests"/> so they share
+/// the same process-wide static state of <see cref="EmailSender.LazyProvider"/>.
+/// </summary>
+[CollectionDefinition(Name)]
+public sealed class EmailSenderCollection : ICollectionFixture<EmailSenderFixture>
+{
+    public const string Name = "EmailSender";
+}
+
+/// <summary>
+/// Fixture that connects <see cref="EmailSender"/> once before all tests in the collection run.
+/// </summary>
+public sealed class EmailSenderFixture
+{
+    public EmailSenderFixture()
+    {
+        // EmailSender is a static class with a Lazy<IServiceProvider>.
+        // ConnectRabbitMq can only be called successfully once per process.
+        if (!EmailSender.IsConnected)
+        {
+            EmailSender.ConnectRabbitMq(cfg =>
+            {
+                cfg.HostName = RabbitMqTestConfig.HostName;
+                cfg.Port = RabbitMqTestConfig.Port;
+                cfg.UserName = RabbitMqTestConfig.UserName;
+                cfg.Password = RabbitMqTestConfig.Password;
+                cfg.VirtualHost = RabbitMqTestConfig.VirtualHost;
+                cfg.QueueName = RabbitMqTestConfig.QueueName;
+                cfg.ExchangeName = RabbitMqTestConfig.ExchangeName;
+                cfg.RoutingKey = RabbitMqTestConfig.RoutingKey;
+                cfg.DlqQueueName = RabbitMqTestConfig.DlqQueueName;
+                cfg.DlqExchangeName = RabbitMqTestConfig.DlqExchangeName;
+                cfg.DlqRoutingKey = RabbitMqTestConfig.DlqRoutingKey;
+            });
+        }
+    }
+}
+
+/// <summary>
+/// Integration tests for the <see cref="EmailSender"/> static client.
+/// All tests run inside <see cref="EmailSenderCollection"/> to share the single
+/// static connection established by <see cref="EmailSenderFixture"/>.
+/// </summary>
+[Collection(EmailSenderCollection.Name)]
+public sealed class EmailSenderTests
+{
+    [Fact]
+    public void IsConnected_AfterConnectRabbitMq_ReturnsTrue()
+    {
+        Assert.True(EmailSender.IsConnected);
+    }
+
+    [Fact]
+    public void ConnectRabbitMq_WhenAlreadyConnected_WithThrowException_ThrowsInvalidOperationException()
+    {
+        Assert.Throws<InvalidOperationException>(() =>
+            EmailSender.ConnectRabbitMq(cfg => { }, OnReconnect.ThrowException));
+    }
+
+    [Fact]
+    public void ConnectRabbitMq_WhenAlreadyConnected_WithIgnore_DoesNotThrow()
+    {
+        var exception = Record.Exception(() =>
+            EmailSender.ConnectRabbitMq(cfg => { }, OnReconnect.Ignore));
+
+        Assert.Null(exception);
+    }
+
+    [Fact]
+    public void Send_WithValidEmail_DoesNotThrow()
+    {
+        var email = new OutgoingEmailEvent
+        {
+            Id = Guid.NewGuid(),
+            Recipient = "hakanttek@gmail.com",
+            Subject = "EmailSender.Send Integration Test",
+            Body = "<p>Sent via EmailSender static client.</p>",
+            IsHtml = true,
+            QueuedAt = DateTime.Now
+        };
+
+        var exception = Record.Exception(() => EmailSender.Send(email));
+
+        Assert.Null(exception);
+    }
+
+    [Fact]
+    public void Send_WithPlainTextBody_DoesNotThrow()
+    {
+        var email = new OutgoingEmailEvent
+        {
+            Id = Guid.NewGuid(),
+            Recipient = "hakanttek@gmail.com",
+            Subject = "Plain Text Test",
+            Body = "This is a plain text email.",
+            IsHtml = false,
+            QueuedAt = DateTime.Now
+        };
+
+        var exception = Record.Exception(() => EmailSender.Send(email));
+
+        Assert.Null(exception);
+    }
+}