Returns information about a stream, including the current status of the
stream, its Amazon Resource Name (ARN), the composition of its shards,
and its corresponding DynamoDB table.
You can call DescribeStream at a maximum rate of 10 times per second.
Each shard in the stream has a SequenceNumberRange associated with it.
If the SequenceNumberRange has a StartingSequenceNumber but no
EndingSequenceNumber, then the shard is still open (able to receive
more stream records). If both StartingSequenceNumber and
EndingSequenceNumber are present, then that shard is closed and can no
longer receive more data.