Extended `DocReceiverElementDto` to include an optional `Document` reference. Enhanced `ReadDocReceiverElementQuery` with `Id` and `IncludeDocument` properties for filtering and document inclusion.
Updated `ReadDocReceiverElementQueryHandler` to handle new query properties, enabling filtering by `Id` and optionally including associated documents.
Introduced `SignPdfByElementCommand` and its handler to support signing PDFs using either a provided `DocReceiverElementDto` or an `ElementId`. Added validation via `SignPdfByElementCommandValidator` to ensure proper usage.
Refactored and added necessary `using` directives for new dependencies.
Introduced `ReadDocReceiverElementQuery` for retrieving document receiver elements and its corresponding handler. Added necessary `using` directives for dependencies like `AutoMapper`, `MediatR`, and `Microsoft.EntityFrameworkCore`.
The handler dynamically filters `DocReceiverElement` data based on optional query parameters (e.g., `Envelope.Id`, `Envelope.Uuid`, `Receiver.Id`, `Receiver.Signature`) using LINQ. Data is fetched asynchronously and mapped to DTOs using `AutoMapper`.
