Fix some Swiftlint warnings

Author: mojganii

ios/MullvadREST/ApiHandlers/RESTRequestFactory.swift

@@ -16,7 +16,7 @@ extension REST {
         let networkTimeout: Duration
         let bodyEncoder: JSONEncoder
 
-        class func withDefaultAPICredentials(
+        static func withDefaultAPICredentials(
             pathPrefix: String,
             bodyEncoder: JSONEncoder
         ) -> RequestFactory {

ios/MullvadSettings/SettingsManager.swift

@@ -47,12 +47,7 @@ public enum SettingsManager {
 
     public static func getLastUsedAccount() throws -> String {
         let data = try store.read(key: .lastUsedAccount)
-
-        if let string = String(data: data, encoding: .utf8) {
-            return string
-        } else {
-            throw StringDecodingError(data: data)
-        }
+        return String(decoding: data, as: UTF8.self)
     }
 
     public static func setLastUsedAccount(_ string: String?) throws {

ios/MullvadVPN/StorePaymentManager/StorePaymentManager.swift

@@ -44,7 +44,7 @@ final class StorePaymentManager: NSObject, SKPaymentTransactionObserver {
     private var paymentToAccountToken = [SKPayment: String]()
 
     /// Returns true if the device is able to make payments.
-    class var canMakePayments: Bool {
+    static var canMakePayments: Bool {
         SKPaymentQueue.canMakePayments()
     }
 

ios/MullvadVPN/View controllers/SelectLocation/LocationCellViewModel.swift

@@ -80,7 +80,7 @@ extension LocationCellViewModel {
             return false
         }
 
-        var proxyNode = RootLocationNode(children: [node])
+        let proxyNode = RootLocationNode(children: [node])
         let allLocations = Set(proxyNode.flattened.flatMap { $0.locations })
         let hostCount = allLocations.filter { location in
             if case .hostname = location { true } else { false }

ios/MullvadVPN/View controllers/Tunnel/TunnelControlView.swift

@@ -388,7 +388,7 @@ final class TunnelControlView: UIView {
         )
     }
 
-    private class func makeBoldTextLabel(ofSize fontSize: CGFloat, numberOfLines: Int = 1) -> UILabel {
+    private static func makeBoldTextLabel(ofSize fontSize: CGFloat, numberOfLines: Int = 1) -> UILabel {
         let textLabel = UILabel()
         textLabel.translatesAutoresizingMaskIntoConstraints = false
         textLabel.font = UIFont.boldSystemFont(ofSize: fontSize)

ios/MullvadVPNTests/MullvadSettings/APIAccessMethodsTests.swift

@@ -13,11 +13,11 @@ import XCTest
 final class APIAccessMethodsTests: XCTestCase {
     static let store = InMemorySettingsStore<SettingNotFound>()
 
-    override class func setUp() {
+    override static func setUp() {
         SettingsManager.unitTestStore = store
     }
 
-    override class func tearDown() {
+    override static func tearDown() {
         SettingsManager.unitTestStore = nil
     }
 

ios/MullvadVPNTests/MullvadSettings/IPOverrideRepositoryTests.swift

@@ -14,11 +14,11 @@ final class IPOverrideRepositoryTests: XCTestCase {
     static let store = InMemorySettingsStore<SettingNotFound>()
     let repository = IPOverrideRepository()
 
-    override class func setUp() {
+    override static func setUp() {
         SettingsManager.unitTestStore = store
     }
 
-    override class func tearDown() {
+    override static func tearDown() {
         SettingsManager.unitTestStore = nil
     }
 

ios/MullvadVPNTests/MullvadSettings/MigrationManagerTests.swift

@@ -16,11 +16,11 @@ final class MigrationManagerTests: XCTestCase {
     static let store = InMemorySettingsStore<SettingNotFound>()
 
     var manager: MigrationManager!
-    override class func setUp() {
+    override static func setUp() {
         SettingsManager.unitTestStore = store
     }
 
-    override class func tearDown() {
+    override static func tearDown() {
         SettingsManager.unitTestStore = nil
     }
 
@@ -72,7 +72,7 @@ final class MigrationManagerTests: XCTestCase {
 
     func testFailedMigrationResetsSettings() throws {
         let store = Self.store
-        let data = try XCTUnwrap("Migration test".data(using: .utf8))
+        let data = Data("Migration test".utf8)
         try store.write(data, for: .settings)
         try store.write(data, for: .deviceState)
 

ios/MullvadVPNTests/MullvadVPN/TunnelManager/TunnelManagerTests.swift

@@ -27,11 +27,11 @@ class TunnelManagerTests: XCTestCase {
 
     var transportProvider: TransportProvider!
 
-    override class func setUp() {
+    override static func setUp() {
         SettingsManager.unitTestStore = store
     }
 
-    override class func tearDown() {
+    override static func tearDown() {
         SettingsManager.unitTestStore = nil
     }
 

ios/PacketTunnelCore/Pinger/Pinger.swift

@@ -217,7 +217,7 @@ public final class Pinger: PingerProtocol {
         }
     }
 
-    private class func makeIPAddress(from sa: sockaddr) -> IPAddress? {
+    private static func makeIPAddress(from sa: sockaddr) -> IPAddress? {
         if sa.sa_family == AF_INET {
             return withUnsafeBytes(of: sa) { buffer -> IPAddress? in
                 buffer.bindMemory(to: sockaddr_in.self).baseAddress.flatMap { boundPointer in