[Shared] Adds @UserInfoValue property wrapper for ALTLocalizedErrors

ALTLocalizedErrors now automatically include all properties annotated with @UserInfoValue in userInfo when bridged to NSError.

Shared/Errors/UserInfoValue.swift

@@ -0,0 +1,38 @@
+//
+//  UserInfoValue.swift
+//  AltStore
+//
+//  Created by Riley Testut on 5/2/23.
+//  Copyright © 2023 Riley Testut. All rights reserved.
+//
+
+import Foundation
+
+protocol UserInfoValueProtocol<Value>
+{
+    associatedtype Value
+    
+    var key: String? { get }
+    var wrappedValue: Value { get }
+}
+
+@propertyWrapper
+public struct UserInfoValue<Value>: UserInfoValueProtocol
+{
+    public let key: String?
+    public var wrappedValue: Value
+    
+    // Necessary for memberwise initializers to work as expected
+    // https://github.com/apple/swift-evolution/blob/main/proposals/0258-property-wrappers.md#memberwise-initializers
+    public init(wrappedValue: Value)
+    {
+        self.wrappedValue = wrappedValue
+        self.key = nil
+    }
+    
+    public init(wrappedValue: Value, key: String)
+    {
+        self.wrappedValue = wrappedValue
+        self.key = key
+    }
+}