Save automatically, improve mocks

CHDataManagement/Storage/ChangeObservableItem.swift

@@ -0,0 +1,31 @@
+import Combine
+
+protocol ChangeObservableItem: ObservableObject {
+
+    var cancellables: Set<AnyCancellable> { get set }
+
+    func needsSaving()
+}
+
+protocol ObservableContentItem: ChangeObservableItem {
+
+    var content: Content { get }
+}
+
+extension ObservableContentItem {
+
+    func needsSaving() {
+        content.needsSave()
+    }
+}
+
+extension ChangeObservableItem {
+
+    func observeChanges() {
+        objectWillChange
+            .sink { [weak self] _ in
+                self?.needsSaving()
+            }
+            .store(in: &cancellables)
+    }
+}