Create optional docker service for syncing production db backups --> s3

[spwoodcock]

Is your feature request related to a problem? Please describe.

• Following on from: Consider plain SQL output for database backups #1307
• In order to have the best tradeoff between flexibility / integrity, we should store custom format SQL dumps in S3.

Describe the solution you'd like

• A small docker service that runs on an interval (and Kubernetes equivalent CronJob in the Helm chart).
• The service should rsync the content of the fmtm-backups local Minio bucket to an external S3 service.
• A good candidate would be AWS s3://hotosm-backups.

Alternatives considered

• Instead of a docker service, this could be via a cron on the host machine. This is not ideal, as it's machine specific config and not portable by default for migration.
• We could sync to anything else! There are many options here.