refactor: update dependencies and remove unused code

- Added new dependencies: `adler2`, `crc32fast`, `flate2`, `miniz_oxide`, and `libredox`.
- Updated existing dependencies: `tokio-rustls` to version 0.26.4 and `filetime` to version 0.2.27.
- Removed the `backup.rs` file as it is no longer needed.
- Introduced tests for configuration and credential management.
- Enhanced the `identity` module to generate W3C compliant DID documents.

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

core/archipelago/src/state.rs

@@ -70,3 +70,117 @@ impl Default for StateManager {
         Self::new()
     }
 }
+
+#[cfg(test)]
+mod tests {
+    use super::*;
+    use crate::data_model::DataModel;
+
+    #[test]
+    fn test_state_manager_new() {
+        let sm = StateManager::new();
+        // Should be constructible without panic
+        let _ = sm.subscribe();
+    }
+
+    #[test]
+    fn test_state_manager_default() {
+        let sm = StateManager::default();
+        let _ = sm.subscribe();
+    }
+
+    #[tokio::test]
+    async fn test_get_snapshot_initial_revision_zero() {
+        let sm = StateManager::new();
+        let (data, rev) = sm.get_snapshot().await;
+        assert_eq!(rev, 0);
+        // DataModel::new() sets version from CARGO_PKG_VERSION
+        assert_eq!(data.server_info.version, env!("CARGO_PKG_VERSION"));
+        assert!(data.package_data.is_empty());
+        assert!(data.notifications.is_empty());
+    }
+
+    #[tokio::test]
+    async fn test_update_data_increments_revision() {
+        let sm = StateManager::new();
+
+        let (_, rev0) = sm.get_snapshot().await;
+        assert_eq!(rev0, 0);
+
+        sm.update_data(DataModel::new()).await;
+        let (_, rev1) = sm.get_snapshot().await;
+        assert_eq!(rev1, 1);
+
+        sm.update_data(DataModel::new()).await;
+        let (_, rev2) = sm.get_snapshot().await;
+        assert_eq!(rev2, 2);
+    }
+
+    #[tokio::test]
+    async fn test_update_data_stores_new_data() {
+        let sm = StateManager::new();
+
+        let mut new_data = DataModel::new();
+        new_data.server_info.name = Some("TestNode".to_string());
+        new_data.ui.theme = "light".to_string();
+        sm.update_data(new_data).await;
+
+        let (snapshot, _) = sm.get_snapshot().await;
+        assert_eq!(snapshot.server_info.name, Some("TestNode".to_string()));
+        assert_eq!(snapshot.ui.theme, "light");
+    }
+
+    #[tokio::test]
+    async fn test_subscribe_receives_updates() {
+        let sm = StateManager::new();
+        let mut rx = sm.subscribe();
+
+        let mut data = DataModel::new();
+        data.server_info.name = Some("BroadcastTest".to_string());
+        sm.update_data(data).await;
+
+        let msg = rx.recv().await.unwrap();
+        assert_eq!(msg.rev, 1);
+        assert!(msg.data.is_some());
+        let received_data = msg.data.unwrap();
+        assert_eq!(received_data.server_info.name, Some("BroadcastTest".to_string()));
+    }
+
+    #[tokio::test]
+    async fn test_multiple_subscribers_receive_same_update() {
+        let sm = StateManager::new();
+        let mut rx1 = sm.subscribe();
+        let mut rx2 = sm.subscribe();
+
+        sm.update_data(DataModel::new()).await;
+
+        let msg1 = rx1.recv().await.unwrap();
+        let msg2 = rx2.recv().await.unwrap();
+        assert_eq!(msg1.rev, msg2.rev);
+        assert_eq!(msg1.rev, 1);
+    }
+
+    #[tokio::test]
+    async fn test_get_initial_message() {
+        let sm = StateManager::new();
+
+        let mut data = DataModel::new();
+        data.server_info.name = Some("InitMsg".to_string());
+        sm.update_data(data).await;
+
+        let msg = sm.get_initial_message().await;
+        assert_eq!(msg.rev, 1);
+        assert!(msg.data.is_some());
+        assert!(msg.patch.is_none());
+        assert_eq!(msg.data.unwrap().server_info.name, Some("InitMsg".to_string()));
+    }
+
+    #[tokio::test]
+    async fn test_update_without_subscribers_does_not_panic() {
+        let sm = StateManager::new();
+        // No subscribers — send should silently succeed
+        sm.update_data(DataModel::new()).await;
+        let (_, rev) = sm.get_snapshot().await;
+        assert_eq!(rev, 1);
+    }
+}