Updated `using` directives to include `DigitalData.Core.Exceptions` for enhanced exception handling. Updated the `[Obsolete]` attribute message to reflect PSPDFKit library deprecation. Renamed `cancellationToken` to `cancel` for consistency.
Added validation to ensure `PsPdfKitAnnotation` is only supported for the `LegacyWeb` receiver type. Introduced stricter checks for missing or invalid annotation data, throwing `BadRequestException` when necessary. Updated `await next` calls to use the renamed parameter.
These changes improve code clarity, enforce stricter validation, and enhance error handling.
Introduced the `SaveSignatureBehavior` class as a pipeline behavior for handling `SigningCommand` requests. Added necessary `using` directives to include required namespaces. Resolved merge conflicts in `using` directives between `net8.0` and `net9.0` project versions. Implemented the `Handle` method to delegate request processing.
