make queue/stream configurable

Right now this library uses `DynamoDB` as queue system to limit the access to the PgSTAC Database.

If used outside the AWS environment it would be nice to be able to *select* a different queuing system (e.g Redis)

Start by locating the DynamoDB queue implementation used to limit access to the pgSTAC database, then trace how ingestion selects and invokes it. Compare the existing behavior with the requested configurable queue, such as Redis; done means a non-AWS queue can be selected while the current DynamoDB behavior remains available.

Written by the indexing model from the issue text.