Create an API for getting submission counts based upon different statuses

**Description:**
Currently, we have the APIs for fetching & deleting the messages from SQS Queue but the challenge host doesn't know the pending messages in the AWS SQS queue.

**Deliverables**:
- [x] Add an API for returning the count of the pending messages in SQS Queue.
- [x] Add relevant tests for the API.

**References:**
- https://forums.aws.amazon.com/thread.jspa?threadID=93105