created_at: AwareDatetime = Field(
        default=None,
        nullable=False,
        sa_type=UtcDateTime,
        sa_column_kwargs={
            "server_default": func.now(),
        },
    )
    updated_at: AwareDatetime = Field(
        default=None,
        nullable=False,  # ①
        sa_type=UtcDateTime,
        sa_column_kwargs={
            "server_default": func.now(),
            "onupdate": lambda: datetime.now(timezone.utc),
        },
    )