[AltKit] Replaces dedicated AltKit module with shared files across targets

Treating AltKit as a full module resulted in more complexity than necessary, when we really just wanted to share some files between different targets. Now we can share individual files across modules as-needed without AltKit overhead.

Shared/Extensions/ALTServerError+Conveniences.swift

@@ -0,0 +1,36 @@
+//
+//  ALTServerError+Conveniences.swift
+//  AltKit
+//
+//  Created by Riley Testut on 6/4/20.
+//  Copyright © 2020 Riley Testut. All rights reserved.
+//
+
+import Foundation
+
+public extension ALTServerError
+{
+    init<E: Error>(_ error: E)
+    {
+        switch error
+        {
+        case let error as ALTServerError: self = error
+        case is DecodingError: self = ALTServerError(.invalidRequest, underlyingError: error)
+        case is EncodingError: self = ALTServerError(.invalidResponse, underlyingError: error)
+        case let error as NSError:
+            var userInfo = error.userInfo
+            if !userInfo.keys.contains(NSUnderlyingErrorKey)
+            {
+                // Assign underlying error (if there isn't already one).
+                userInfo[NSUnderlyingErrorKey] = error
+            }
+            
+            self = ALTServerError(.underlyingError, userInfo: userInfo)
+        }
+    }
+    
+    init<E: Error>(_ code: ALTServerError.Code, underlyingError: E)
+    {
+        self = ALTServerError(code, userInfo: [NSUnderlyingErrorKey: underlyingError])
+    }
+}