Introduced interfaces for audit fields (AddedWhen, ChangedWhen, ChangedWho, AddedWho) and updated domain entities to implement them. Adjusted properties for consistency and nullability. Updated MappingProfile to map audit fields between DTOs and entities. Improves auditability and standardization across the domain model.
- Moved file-related properties (Filename, Filepath, FileNameOriginal) into dedicated region
- Added column mappings for file-related properties
- Changed Elements type to IEnumerable<Signature> for better abstraction
- Adjusted EnvelopeId default initialization for NETFRAMEWORK only
- Updated ByteData and nullable types for NET compatibility
- Removed obsolete default value and simplified property definitions
