Refactored `DocSignedNotification` to remove inheritance from
`EnvelopeReceiverDto` and introduced a required `EnvelopeReceiver`
property. Updated all usages across the codebase to align with the
new structure, including controllers, handlers, and tests.
- Improved encapsulation and reduced coupling by making
dependencies explicit.
- Updated `AnnotationController`, `DocStatusHandler`,
`HistoryHandler`, and `SendSignedMailHandler` to use the
`EnvelopeReceiver` property.
- Adjusted `DocSignedNotificationTests` to reflect the new
instantiation pattern.
- Updated XML documentation and ensured consistent access to
`EnvelopeReceiver` properties like `EnvelopeId`, `ReceiverId`,
and `EmailAddress`.
Added logic to set email template placeholders based on whether the envelope requires "Read and Confirm" or "Sign" actions. Placeholders such as [SIGNATURE_TYPE], [DOCUMENT_PROCESS], [FINAL_STATUS], [FINAL_ACTION], [REJECTED_BY_OTHERS], and [RECEIVER_ACTION] are now dynamically set to reflect the correct process and status, improving the accuracy and clarity of notification emails.
