WorkflowDraftVariable
- Introduce `WorkflowDraftVariable` model and the corresponding migration. - Implement `EnumText`, a custom column type for SQLAlchemy designed to work seamlessly with enumeration classes based on `StrEnum`.
Signed-off-by: -LAN- <laipz8200@outlook.com> Co-authored-by: Copilot <175728472+Copilot@users.noreply.github.com>