Todo repository protocol (#8)

This PR contains the work done to decouple the direct use of the `ModelContext` from `SwiftData` from the view model that uses it. In addition, the project transitioned to use Swift 6 and strict concurrency which brought some issues with the unit tests, so they were amended as well.

Reviewed-on: rock-n-code/todos-app#8
Co-authored-by: Javier Cicchelli <javier@rock-n-code.com>
Co-committed-by: Javier Cicchelli <javier@rock-n-code.com>

App/Sources/View Models/NewTaskViewModel.swift

@@ -57,14 +57,14 @@ extension NewTaskView {
 
         // MARK: Functions
 
-        /// Saves a new todo task to the SwiftData model context.
+        /// Saves a new todo task to the repository.
         ///
-        /// This function creates a new `Todo` instance with the current property values and inserts it into the provided model context.
+        /// This function creates a new `Todo` instance with the current property values and inserts it into the provided repository.
         /// The title and note are trimmed of leading and trailing whitespace before saving.
         /// The `note` property value is only included if it's not empty after trimming.
         ///
-        /// - Parameter modelContext: The SwiftData model context to insert a new todo task.
-        func save(to modelContext: ModelContext) {
+        /// - Parameter repository: The repository to insert a new todo task.
+        func save(to repository: TodoRepository) {
             let trimmedTitle = title.trimmingCharacters(in: .whitespacesAndNewlines)
             let trimmedNote = note.trimmingCharacters(in: .whitespacesAndNewlines)
 
@@ -74,7 +74,7 @@ extension NewTaskView {
                 due: due
             )
 
-            modelContext.insert(todo)
+            repository.insert(todo)
         }
 
     }