Add PreviewManger with Core Data cache and a URLPreviewView with a view model.

Changes to RoomDataSource still to come.

Riot/Managers/URLPreviews/URLPreviewCacheData.swift

@@ -0,0 +1,43 @@
+// 
+// Copyright 2021 New Vector Ltd
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+// http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+//
+
+import CoreData
+
+extension URLPreviewCacheData {
+    convenience init(context: NSManagedObjectContext, preview: URLPreviewViewData, creationDate: Date) {
+        self.init(context: context)
+        update(from: preview, on: creationDate)
+    }
+    
+    func update(from preview: URLPreviewViewData, on date: Date) {
+        url = preview.url
+        siteName = preview.siteName
+        title = preview.title
+        text = preview.text
+        image = preview.image
+        
+        creationDate = date
+    }
+    
+    func preview() -> URLPreviewViewData? {
+        guard let url = url else { return nil }
+        
+        let viewData = URLPreviewViewData(url: url, siteName: siteName, title: title, text: text)
+        viewData.image = image as? UIImage
+        
+        return viewData
+    }
+}