Faster S3 file Source for Structured Streaming with SQS

Using FileStreamSource to read files from a S3 bucket has problems both in terms of costs and latency:

• Latency: Listing all the files in S3 buckets every microbatch can be both slow and resource intensive.
• Costs: Making List API requests to S3 every microbatch can be costly.

The solution is to use Amazon Simple Queue Service (SQS) which lets you find new files written to S3 bucket without the need to list all the files every microbatch.

S3 buckets can be configured to send notification to an Amazon SQS Queue on Object Create / Object Delete events. For details see AWS documentation here Configuring S3 Event Notifications 

Spark can leverage this to find new files written to S3 bucket by reading notifications from SQS queue instead of listing files every microbatch.

I hope to contribute changes proposed in this pull request to Apache Bahir as suggested by gaborgsomogyi  here