Azure Cosmos DB now provides the ability to access the change feed (https://docs.microsoft.com/en-us/azure/cosmos-db/change-feed). A common pattern to implement eventing patterns is
1. Store every version/change as a separate item
2. Read the change feed to merge/consolidate changes and trigger appropriate actions downstream.
You can also expire old versions using TTL: https://docs.microsoft.com/en-us/azure/cosmos-db/time-to-live