Introduce KeyImporter protocol to reduce code duplications in SSH key importers

pass/Controllers/KeyImporter.swift

@@ -0,0 +1,36 @@
+//
+//  KeyImporter.swift
+//  pass
+//
+//  Created by Danny Moesch on 15.02.20.
+//  Copyright © 2020 Bob Sun. All rights reserved.
+//
+
+import passKit
+
+protocol KeyImporter {
+
+    static var keySource: KeySource { get }
+
+    static var label: String { get }
+
+    static var menuLabel: String { get }
+
+    func isReadyToUse() -> Bool
+
+    func importKeys() throws
+}
+
+extension KeyImporter {
+
+    static var isCurrentKeySource: Bool {
+        return Defaults.gitSSHKeySource == Self.keySource
+    }
+
+    static var menuLabel: String {
+        if isCurrentKeySource {
+            return "✓ \(Self.label)"
+        }
+        return Self.label
+    }
+}