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/Protocols/TodoRepository.swift

@@ -0,0 +1,28 @@
+import SwiftData
+
+/// A protocol defining the interface for a todo repository.
+///
+/// This protocol abstracts the underlying data persistence mechanism for todo tasks,
+/// allowing for dependency injection and easier testing. Implementations handle the
+/// storage and retrieval of Todo objects.
+protocol TodoRepository {
+
+    /// Deletes a todo task from the repository.
+    ///
+    /// This method removes the specified todo from persistent storage. The deletion
+    /// is typically performed immediately, though the actual persistence may be deferred
+    /// until a save operation occurs depending on the implementation.
+    ///
+    /// - Parameter todo: The todo task to delete from the repository.
+    func delete(_ todo: Todo)
+
+    /// Inserts a new todo task into the repository.
+    ///
+    /// This method adds a new todo to persistent storage. The todo is typically
+    /// tracked immediately, though the actual persistence may be deferred until a
+    /// save operation occurs depending on the implementation.
+    ///
+    /// - Parameter todo: The todo task to insert into the repository.
+    func insert(_ todo: Todo)
+
+}