added helper functions

MVMCore/MVMCore/Models/JSON/JSONHelper.swift

@@ -15,4 +15,47 @@ public enum JSONError: Error {
     case pathNotFound
     case data(path: String)
     case other(error: Error)
+    case error(message: String)
+}
+
+extension JSONDictionary  {
+    
+    public func toJSONString(options: JSONSerialization.WritingOptions = []) -> String? {
+        guard let data = try? JSONSerialization.data(withJSONObject: self, options: options),
+              let string = String(data: data, encoding: .utf8) else {
+                  return nil
+              }
+        return string
+    }
+    
+    public func toUrlQueryItems() throws -> [URLQueryItem] {
+        var queryItems: [URLQueryItem] = []
+        for (key, value) in self {
+            var valueString: String
+            if let value = value as? JSONDictionary, let jsonString = value.toJSONString() {
+                valueString = jsonString
+            } else if let value = value as? [AnyHashable], let jsonString = value.toJSONString() {
+                valueString = jsonString
+            } else {
+                guard let baseValueString = String(describing: value.base).removingPercentEncoding else {
+                    throw JSONError.error(message: "query item failed: \(key) value \(value.base)")
+                }
+                valueString = baseValueString
+            }
+            let queryItem = URLQueryItem(name: key, value: valueString)
+            queryItems.append(queryItem)
+        }
+        return queryItems
+    }
+}
+
+extension Array where Element == AnyHashable  {
+    
+    public func toJSONString(options: JSONSerialization.WritingOptions = []) -> String? {
+        guard let data = try? JSONSerialization.data(withJSONObject: self, options: options),
+              let string = String(data: data, encoding: .utf8) else {
+                  return nil
+              }
+        return string
+    }
 }