Introduced four new pipeline behaviors (`AnnotationBehavior`,
`DocStatusBehavior`, `HistoryBehavior`, and `SendSignedMailBehavior`)
to modularize the signing process. These behaviors handle annotation
persistence, document status creation, history recording, and signed
mail notifications, respectively.
- `AnnotationBehavior`: Saves annotations using `IRepository`.
- `DocStatusBehavior`: Creates document status via `ISender`.
- `HistoryBehavior`: Records signing history and validates receiver
information.
- `SendSignedMailBehavior`: Sends signed mail notifications using
email templates and dynamic placeholder replacement.
Added error handling for missing data in `HistoryBehavior` and
`SendSignedMailBehavior`. Updated the signing pipeline to execute
these behaviors sequentially, ensuring a structured and extensible
workflow.
