feat: add unit tests for models and ListStore and UI test for adding a todo

MindDump/MindDumpApp.swift

@@ -7,7 +7,11 @@ struct MindDumpApp: App {
     @State private var store: ListStore
 
     init() {
-        let container = try! ModelContainer(for: TodoList.self, TodoItem.self)
+        let isUITest = ProcessInfo.processInfo.arguments.contains("UI_TESTING")
+        let config = isUITest
+            ? ModelConfiguration(isStoredInMemoryOnly: true)
+            : ModelConfiguration()
+        let container = try! ModelContainer(for: TodoList.self, TodoItem.self, configurations: config)
         self.container = container
         self._store = State(initialValue: ListStore(modelContext: container.mainContext))
     }