Replaced `DigitalData.MessagingService.Client.DependencyInjection`
namespace with `DigitalData.MessagingService.Client` across the
codebase to simplify and streamline the project structure.
Removed unused `Microsoft.Extensions.Logging` and `System`
dependencies from `EmailSender.cs`. Updated project references
in `DigitalData.MessagingService.Tests.csproj` to reflect the
namespace and project restructuring. Adjusted `using` directives
in test files to align with the new namespace.
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.
