Migrate Airflow database during SPS deployment

[LucaCinquini]

Purpose

• This PR supports backing up and restoring the Airflow database during an SPS redeployment. Additionally, the Airflow database will now be automatically backed-up daily, and each back-up retained for 7 days.

Proposed Changes

• [ADD] Final snapshot of the Postgres database automatically created and restored.
• [ADD] Daily backups of the Postgres database, with 7 days retention period.

Issues

• Migrate database content during SPS upgrades

Testing

• Deployed the SPS, executed a few DAGs, destroyed the SPS, redeployed the SPS and re-published the DAGs through the OGC API. The previous DAG instance runs were retained.
• Also verified that automatic backups were created nightly.

[nikki-t]

This looks good to me. I don't have a ton of experience with managing database instances in terraform. So to check my understanding, it looks like the check_rds_snapshot.sh script is used to determine if an RDS snapshot exists which sets the data source for the snapshot. This data source is then used as the snapshot identifier in the aws_db_instance resource which has also been modified to include snapshots. It seems like the snapshot identifier specifies whether to create the database from a snapshot which allows it to be restored after being destroyed. If I have got that right, I think this covers migrating the database during deployments!

[LucaCinquini]

You got that right Nikki, thanks for reviewing and approving the PR.