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/EmailSenderUrlOverloadTests.cs

@@ -0,0 +1,74 @@
+using DigitalData.MessagingService.Client.DependencyInjection;
+using DigitalData.MessagingService.Publisher.Abstraction;
+
+namespace DigitalData.MessagingService.Tests.Integration;
+
+/// <summary>
+/// Integration tests for the URL-based <see cref="EmailSender.ConnectRabbitMq(string, string, string, OnReconnect)"/>
+/// overload. All tests run inside <see cref="EmailSenderCollection"/> so they share the already-established
+/// static connection. The URL overload is exercised via <see cref="OnReconnect.Ignore"/> and
+/// <see cref="OnReconnect.ThrowException"/> to verify its delegation and guard behavior.
+/// </summary>
+[Collection(EmailSenderCollection.Name)]
+public sealed class EmailSenderUrlOverloadTests
+{
+    private static readonly string ValidUrl = $"amqp://{RabbitMqTestConfig.HostName}:{RabbitMqTestConfig.Port}";
+    private static readonly string ValidUrlWithVHost = $"amqp://{RabbitMqTestConfig.HostName}:{RabbitMqTestConfig.Port}/myvhost";
+
+    [Fact]
+    public void ConnectRabbitMq_UrlOverload_WhenAlreadyConnected_WithIgnore_DoesNotThrow()
+    {
+        var exception = Record.Exception(() =>
+            EmailSender.ConnectRabbitMq(
+                ValidUrl,
+                RabbitMqTestConfig.UserName,
+                RabbitMqTestConfig.Password,
+                OnReconnect.Ignore));
+
+        Assert.Null(exception);
+    }
+
+    [Fact]
+    public void ConnectRabbitMq_UrlOverload_WhenAlreadyConnected_WithThrowException_Throws()
+    {
+        Assert.Throws<InvalidOperationException>(() =>
+            EmailSender.ConnectRabbitMq(
+                ValidUrl,
+                RabbitMqTestConfig.UserName,
+                RabbitMqTestConfig.Password,
+                OnReconnect.ThrowException));
+    }
+
+    [Fact]
+    public void ConnectRabbitMq_UrlOverload_WithVHostInPath_WithIgnore_DoesNotThrow()
+    {
+        var exception = Record.Exception(() =>
+            EmailSender.ConnectRabbitMq(
+                ValidUrlWithVHost,
+                RabbitMqTestConfig.UserName,
+                RabbitMqTestConfig.Password,
+                OnReconnect.Ignore));
+
+        Assert.Null(exception);
+    }
+
+    [Fact]
+    public void Send_AfterUrlOverloadConnection_DoesNotThrow()
+    {
+        var email = new OutgoingEmailEvent
+        {
+            Id = Guid.NewGuid(),
+            Recipient = "url-overload-test@example.com",
+            Subject = "URL Overload Integration Test",
+            Body = "<p>Sent after URL-based connection.</p>",
+            IsHtml = true,
+            QueuedAt = DateTime.Now
+        };
+
+        // Connection was established via Action<> overload in the fixture;
+        // Send should work regardless of which overload was used to connect.
+        var exception = Record.Exception(() => EmailSender.Send(email));
+
+        Assert.Null(exception);
+    }
+}