Send notifications via IMessagingServiceClient and PublishEmailViaSmtpCommand instead of the static EmailSender. The sender address now comes from NotificationOptions and attachments are added through the command builder.
Rename the Notify parameter to receiverEmail so the call site contract is explicit.
Replace the hard-coded RabbitMQ setup with NotificationOptions bound from a configurable section. The new ConsumerType switch wires either the HTTP API client or the RabbitMQ client, and startup now fails with a clear error when required settings are missing.
Bump DigitalData.MessagingService.Client to 3.0.1 for the abstraction used by both transports.
Introduced `EnvelopeNotificationBase` as a new base class for notifications, providing a unified structure with an abstract `GetTemplateType` method and optional attachments. Added `DocumentReceivedNotification` and updated `DocumentSignedNotification` to inherit from this base class, streamlining attachment handling and template type determination.
Refactored `IEnvelopeNotificationService` to use a generic `Notify` method, allowing for flexibility with different notification types. Updated `FinalizeEnvelopeCommandHandler` to align with the new attachment handling.
Added `EnvelopeNotificationExtensions` for converting attachments to `EmailAttachmentDto` objects and introduced `ReplacePlaceholderExtensions` for dynamic placeholder replacement in email templates using reflection. Removed outdated placeholder logic from `EnvelopeNotificationService`.
