Deploy a Cron Job to Backup PostgreSQL to Amazon S3

This repo is originally forked from https://github.com/render-examples/postgres-s3-backups.

It is deployed as a cron job on Render in the same environment as the database that needs to be backed up.

The following environment variables must be set:

• DATABASE_URL: the internal database URL
• AWS_REGION: AWS region where the S3 bucket that will store the backups is located (probably us-west-2)
• S3_BUCKET_NAME: name of the S3 bucket where the backups will be stored
• AWS_ACCESS_KEY_ID + AWS_SECRET_ACCESS_KEY: AWS credentials for a user that has access to the S3 bucket (and ideally nothing else)
• POSTGRES_VERSION: Postgres version for the DB being backed up. At the time of this writing, we're running Postgres 15 in all environments, so this would be set to 15
• ALPINE_VERSION: Alpine version. 3.20 for Postgres 15 or 16.
• DIR_NAME: top-level directory name where the backups will be stored in S3. Should be the same as the DB instance name on Render, e.g. thatch-db-staging.