Feature-Request: sturctured logging / log-format json

[s256]

Unfortunately go is not a language I am experienced in, but I love your project and wanted to drop the idea of adding a flag to enable structured logging.

In my setup your snapshot agent logs to a file thanks to systemd

ExecStart=/usr/local/bin/vault_raft_snapshot_agent
ExecReload=/usr/local/bin/vault_raft_snapshot_agent
StandardOutput=append:/var/log/vault_snapshots.log

Filebeat is harvesting the file and sends the data to elasticsearch, which is a data source in my grafana.
Backups are run hourly, so if there is no successful backup in the last hour according to the logs, grafana triggers an alert.