FTP/SFTP servers for the reference environments

Overview

The Acquisitions team will soon start work on features that involve uploading files to an FTP/SFTP server.  More specifically, generate a batch voucher and upload it to a configured FTP location w/ the configured credentials.  In order to support testing in the reference environments (folio-testing/snapshot/etc.) we'll need to provision an FTP/SFTP server.  I'm also aware that somewhere on the roadmap are other features which work with FTP, so this is the first but not the only feature requiring something like this.  Examples include EDI/Edifact ordering and invoicing, possibly others too (export?)

There are no requirements for a particular directory structure, or specific user credentials to be provisioned.  I imagine that there's no real need for long-lived data here as it's only for testing purposes.  Periodic aging out or purging of data should be perfectly acceptable for our current needs.

At this point the load is expected to be low so something lightweight is probably fine.

Acceptance criteria

• An FTP server is provisioned and accessible from the reference envs
• An SFTP server is provisioned and accessible from the reference envs
• These are documented on the wiki (https://dev.folio.org/guides/automation/#reference-environments ?)