[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.