Support backups volume mapped to an S3 bucket

[Cooke]

Thanks for a great tool.

I'm using it with a volume mapped to an S3 bucket. Because of this the hard linking in the script fails.

I could probably make a PR if its welcome to optionally use file copy instead of linking?

[prodrigestivill]

Hello @Cooke,

For using with S3 isn't it better to use the original image schickling/postgres-backup-s3?

As it is implemented right now copying would make you use a lot of data usage for your S3, since as it is implemented it would have to upload 3 times the exact same file after each backup.

Maybe a better approach if you still want to use this docker image would be use rclone with the backups volume shared to upload the daily folder to your S3 (or last folder if I finally merge feature/limit-last-backups branch), but don't upload all the files in the backups volume to avoid the issue stated before.

I hope this information helps in your deployment.