Retrieve multiple JSON Document Attributes from DynamoDB

Multiple users have requested the ability to retrieve multiple "JSON Document Attribute" values from AWS DynamoDB. Currently, the GetDynamoDB processor only allows the retrieval of a single document attribute during invocation.

Possible avenues to implement this include a regex for selecting multiple JSON document attributes or a comma-separated enumerated list. The destination of the data is also a concern – currently the response becomes the flowfile content. If multiple keys are queried, perhaps a nested JSON document would be returned into the flowfile content. Or a new processor GetDynamoDBRecord could be introduced which formats the response into NiFi record elements.

[1] https://apachenifi.slack.com/archives/C0L9UPWJZ/p1592595131207000?thread_ts=1592594850.206900&cid=C0L9UPWJZ
[2] https://apachenifi.slack.com/archives/C0L9VCD47/p1592598777338800