[Feature] Support a CosmosDb Outbox

**Problem**
We don't support the Outbox pattern for CosmosDb. increasingly, Azure customers may be using CosmosDb for entities and we should support working with the Outbox and CosmosDb

**Describe the solution you'd like**
- Support for using it with a CosmosDb TransactionalBatch

**Describe alternatives you've considered**
- Consider support for using the CosmosDb Change Feed instead of a TransactionalBatch as the source of writes to the Outbox. This would be a separate process and whilst valuable represents the story after this one
- It's possible that a 'single table' approach works with CosmosDb as well.