## outboxMutationFailed

Dispatched when publishing a mutation fails

HubPayload `outboxMutationFailed` contains:
- `modelName` (String): the name of the model that failed to publish
- `element`:
    - `model` (Model): the model instance that failed to publish
    - `errorType` (MutationErrorType): error type that occurred
    - `operation` (MutationType): type of mutation that failed
