Add sync_changes to CalendarStore

crates/store/src/calendar.rs

@@ -13,3 +13,23 @@ pub struct Calendar {
     pub deleted_at: Option<NaiveDateTime>,
     pub synctoken: i64,
 }
+
+impl Calendar {
+    pub fn format_synctoken(&self) -> String {
+        format_synctoken(self.synctoken)
+    }
+}
+
+const SYNC_NAMESPACE: &str = "github.com/lennart-k/rustical/ns/";
+
+pub fn format_synctoken(synctoken: i64) -> String {
+    format!("{}{}", SYNC_NAMESPACE, synctoken)
+}
+
+pub fn parse_synctoken(synctoken: &str) -> Option<i64> {
+    if !synctoken.starts_with(SYNC_NAMESPACE) {
+        return None;
+    }
+    let (_, synctoken) = synctoken.split_at(SYNC_NAMESPACE.len());
+    synctoken.parse::<i64>().ok()
+}