Introduces ICurrentUserSessionService and its implementation to provide access to the current user's session ID via the 'sid' claim. Registers the service in DI and adds comprehensive unit tests to validate correct and error scenarios.
Renamed IMessageService to IMessageCommandService and updated all usages accordingly. Moved and renamed test files from Govor.API.Tests to the new Govor.Application.Tests project, updating namespaces to match. Refactored message-related services and controllers to use the new naming and structure. Added Govor.Application.Tests project to the solution.