- Added XML documentation to the `Handle` method in `UpdateEmailTemplateCommandHandler`.
- Improved readability in `ReadEmailTemplateQueryHandler` by storing the mapped response in a variable.
- Updated properties in `ReadEmailTemplateResponse` to be mutable and renamed `Type` to `Name` with a type change from `int` to `string`.
- Added data annotations in `EmailTemplate` for `AddedWhen` and introduced a new nullable `ChangedWhen` property.
- Included necessary using directives for data annotations in `EmailTemplate.cs`.
- Updated EmailTemplateDto to allow mutable Body and Subject properties.
- Implemented IRequest interface in UpdateEmailTemplateCommand for MediatR.
- Enhanced error handling in EmailTemplateController with NotFoundException.
- Introduced UpdateEmailTemplateCommandHandler for processing update commands.
- Added NotFoundException class for improved error handling.
