[Library] iTunes library (#5)

This PR contains the work done to implement the `iTunesService` service that fetches the reviews from the **Apple App Store**.

Reviewed-on: rock-n-code/app-reviews#5
Co-authored-by: Javier Cicchelli <javier@rock-n-code.com>
Co-committed-by: Javier Cicchelli <javier@rock-n-code.com>

Libraries/iTunes/Kit/Models/Feed.swift

@@ -0,0 +1,51 @@
+//
+//  Feed.swift
+//  ReviewsiTunesKit
+//
+//  Created by Javier Cicchelli on 17/03/2024.
+//  Copyright © 2024 Röck+Cöde VoF. All rights reserved.
+//
+
+import ReviewsFeedKit
+
+struct Feed {
+    
+    // MARK: Constants
+    let entries: [Review]
+    
+}
+
+// MARK: - Decodable
+extension Feed: Decodable {
+    
+    // MARK: Enumerations
+    enum FeedKeys: String, CodingKey {
+        case feed
+    }
+    
+    enum EntryKeys: String, CodingKey {
+        case entry
+    }
+    
+    // MARK: Initialisers
+    init(from decoder: any Decoder) throws {
+        let feed = try decoder.container(keyedBy: FeedKeys.self)
+        let feedEntry = try feed.nestedContainer(keyedBy: EntryKeys.self, forKey: .feed)
+        
+        self.entries = try feedEntry.decode([Review].self, forKey: .entry)
+    }
+    
+}
+
+// MARK: - Encodable
+extension Feed: Encodable {
+    
+    // MARK: Functions
+    func encode(to encoder: any Encoder) throws {
+        var feed = encoder.container(keyedBy: FeedKeys.self)
+        var feedEntry = feed.nestedContainer(keyedBy: EntryKeys.self, forKey: .feed)
+        
+        try feedEntry.encode(entries, forKey: .entry)
+    }
+    
+}