add backup related types and cmd arguments

- fix some typos & format

src/backups.rs

@@ -0,0 +1,55 @@
+use std::path::PathBuf;
+
+use chrono::{DateTime, Local};
+use serde::{Deserialize, Serialize};
+
+use crate::storages::Storage;
+
+/// Targets for backup source or destination.
+#[derive(Debug, Serialize, Deserialize)]
+pub struct BackupTarget {
+    storage: Storage,
+    path: PathBuf,
+}
+
+/// Type of backup commands.
+#[derive(Debug, Serialize, Deserialize)]
+pub enum BackupCommand {
+    ExternallyInvoked(ExternallyInvoked),
+}
+
+/// Backup commands which is not invoked from xdbm itself.
+/// Call xdbm externally to record backup datetime and status.
+#[derive(Debug, Serialize, Deserialize)]
+pub struct ExternallyInvoked {
+    name: String,
+    pub note: String,
+}
+
+/// Backup execution log.
+#[derive(Debug, Serialize, Deserialize)]
+pub struct BackupLog {
+    datetime: DateTime<Local>,
+    status: BackupResult,
+    log: String,
+}
+
+/// Result of backup.
+#[derive(Debug, Serialize, Deserialize)]
+pub enum BackupResult {
+    Success,
+    Failure,
+}
+
+/// Backup source, destination, command and logs.
+#[derive(Debug, Serialize, Deserialize)]
+pub struct Backup {
+    /// must be unique
+    name: String,
+    /// name of [`crate::Device`]
+    device: String,
+    from: BackupTarget,
+    to: BackupTarget,
+    command: BackupCommand,
+    logs: Vec<BackupLog>,
+}