feat add SRMOperationStatus event model

        if self.status != "failed" and not self.instances:

            raise ValueError("instances is required when status != failed")

        return self

class SRMOperationStatus(BaseModel):

    """`event.srm.operation.status` (srm/interface-contract.md §C.1).

    Covers both pre-execution states (`accepted`, `failed_before_start`) and, per §C.3's

    "backend-driven change" case, post-completion capability condition changes (e.g. a QoD

    session dropped by the network) reusing the original realization's `operation_id`.

    Backend-specific status (e.g. `qos_status`) lives in `metadata`, never in `state`.

    """

    schema_version: str

    operation_id: str

    service_order_id: str | None = None

    service_instance_id: str | None = None

    capability: str | None = None

    state: Literal["accepted", "failed_before_start", "completed", "failed", "in_progress"]

    metadata: dict[str, Any] | None = None

    correlation_id: str

    emitted_at: str