Add DeepL translation integration

Changelog-Added: DeepL translation integration
Closes: #522

damus/Models/TranslationService.swift

@@ -0,0 +1,37 @@
+//
+//  TranslationService.swift
+//  damus
+//
+//  Created by Terry Yiu on 2/3/23.
+//
+
+import Foundation
+
+enum TranslationService: String, CaseIterable, Identifiable {
+    var id: String { self.rawValue }
+
+    struct Model: Identifiable, Hashable {
+        var id: String { self.tag }
+        var tag: String
+        var displayName: String
+    }
+
+    case none
+    case libretranslate
+    case deepl
+
+    var model: Model {
+        switch self {
+        case .none:
+            return .init(tag: self.rawValue, displayName: NSLocalizedString("None", comment: "Dropdown option for selecting no translation service."))
+        case .libretranslate:
+            return .init(tag: self.rawValue, displayName: NSLocalizedString("LibreTranslate (Open Source)", comment: "Dropdown option for selecting LibreTranslate as the translation service."))
+        case .deepl:
+            return .init(tag: self.rawValue, displayName: NSLocalizedString("DeepL (Proprietary, Higher Accuracy)", comment: "Dropdown option for selecting DeepL as the translation service."))
+        }
+    }
+
+    static var allModels: [Model] {
+        return Self.allCases.map { $0.model }
+    }
+}