Add LinkPreview model.

SignalServiceKit/src/Messages/Interactions/LinkPreview.swift

@@ -0,0 +1,36 @@
+//
+//  Copyright (c) 2019 Open Whisper Systems. All rights reserved.
+//
+
+import Foundation
+
+@objc(OWSLinkPreview)
+public class LinkPreview: MTLModel {
+    @objc
+    public var urlString: String?
+
+    @objc
+    public var title: String?
+
+    @objc
+    public var attachmentId: String?
+
+    @objc
+    public init(urlString: String, title: String?, attachmentId: String?) {
+        self.urlString = urlString
+        self.title = title
+        self.attachmentId = attachmentId
+
+        super.init()
+    }
+
+    @objc
+    public required init!(coder: NSCoder) {
+        super.init(coder: coder)
+    }
+
+    @objc
+    public required init(dictionary dictionaryValue: [AnyHashable: Any]!) throws {
+        try super.init(dictionary: dictionaryValue)
+    }
+}