Runs an isolated, sandboxed SFTP server that only interacts with virtual backing storage on Google Cloud Storage (GCS).
Set the following environment variables, e.g.
SFTP_USERNAME=user123
SFTP_PASSWORD=kl5dfqpw3NXCZX0
SFTP_PORT=2022
SFTP_SERVER_KEY_PATH=/id_rsa
GCS_CREDENTIALS_FILE=/credentials.json
GCS_BUCKET=my-sftp-bucket
GET, PUT, STAT, LIST & MKDIR are currently the only methods implemented.