Remove unused messaging system (#3047)

Task/Issue URL: https://app.asana.com/0/1199230911884351/1207938980070863/f
Tech Design URL:
CC:

Description:

This PR removes the now-unused messaging system from the app.

DuckDuckGo/Application/AppDelegate.swift

@@ -396,6 +396,10 @@ final class AppDelegate: NSObject, NSApplicationDelegate {
 
         remoteMessagingClient?.startRefreshingRemoteMessages()
 
+        // This messaging system has been replaced by RMF, but we need to clean up the message manifest for any users who had it stored.
+        let deprecatedRemoteMessagingStorage = DefaultSurveyRemoteMessagingStorage.surveys()
+        deprecatedRemoteMessagingStorage.removeStoredMessagesIfNecessary()
+
         if didCrashDuringCrashHandlersSetUp {
             PixelKit.fire(GeneralPixel.crashOnCrashHandlersSetUp)
             didCrashDuringCrashHandlersSetUp = false

DuckDuckGo/Common/Surveys/HomePageRemoteMessagingStorage.swift

@@ -20,9 +20,6 @@ import Foundation
 
 protocol SurveyRemoteMessagingStorage {
 
-    func store(messages: [SurveyRemoteMessage]) throws
-    func storedMessages() -> [SurveyRemoteMessage]
-
     func dismissRemoteMessage(with id: String)
     func dismissedMessageIDs() -> [String]
 
@@ -61,24 +58,6 @@ final class DefaultSurveyRemoteMessagingStorage: SurveyRemoteMessagingStorage {
         self.dismissedMessageIdentifiersKey = dismissedMessageIdentifiersKey
     }
 
-    func store(messages: [SurveyRemoteMessage]) throws {
-        let encoded = try JSONEncoder().encode(messages)
-        try encoded.write(to: messagesURL)
-    }
-
-    func storedMessages() -> [SurveyRemoteMessage] {
-        do {
-            let messagesData = try Data(contentsOf: messagesURL)
-            let messages = try JSONDecoder().decode([SurveyRemoteMessage].self, from: messagesData)
-
-            return messages
-        } catch {
-            // Errors can occur if the file doesn't exist or the schema changed, in which case the app will fetch the file again later and
-            // overwrite it.
-            return []
-        }
-    }
-
     func dismissRemoteMessage(with id: String) {
         var dismissedMessages = dismissedMessageIDs()
 
@@ -95,6 +74,10 @@ final class DefaultSurveyRemoteMessagingStorage: SurveyRemoteMessagingStorage {
         return messages ?? []
     }
 
+    func removeStoredMessagesIfNecessary() {
+        try? FileManager.default.removeItem(at: messagesURL)
+    }
+
     func removeStoredAndDismissedMessages() {
         userDefaults.removeObject(forKey: dismissedMessageIdentifiersKey)
         try? FileManager.default.removeItem(at: messagesURL)