Move private helper structs out of WFClient file

Sources/WriteFreely/Helpers.swift

@@ -0,0 +1,36 @@
+import Foundation
+
+struct ServerData<T: Decodable>: Decodable {
+    enum CodingKeys: String, CodingKey {
+        case code
+        case data
+    }
+
+    init(from decoder: Decoder) throws {
+        let container = try decoder.container(keyedBy: CodingKeys.self)
+        code = try container.decode(Int.self, forKey: .code)
+        data = try container.decode(T.self, forKey: .data)
+    }
+
+    let code: Int
+    let data: T
+}
+
+struct NestedPostsJson: Decodable {
+    enum CodingKeys: String, CodingKey {
+        case code
+        case data
+
+        enum PostKeys: String, CodingKey {
+            case posts
+        }
+    }
+
+    init(from decoder: Decoder) throws {
+        let container = try decoder.container(keyedBy: CodingKeys.self)
+        let postsContainer = try container.nestedContainer(keyedBy: CodingKeys.PostKeys.self, forKey: .data)
+        data = try postsContainer.decode([WFPost].self, forKey: .posts)
+    }
+
+    let data: [WFPost]
+}

Sources/WriteFreely/WFClient.swift

@@ -1,40 +1,5 @@
 import Foundation
 
-struct ServerData<T: Decodable>: Decodable {
-    enum CodingKeys: String, CodingKey {
-        case code
-        case data
-    }
-
-    init(from decoder: Decoder) throws {
-        let container = try decoder.container(keyedBy: CodingKeys.self)
-        code = try container.decode(Int.self, forKey: .code)
-        data = try container.decode(T.self, forKey: .data)
-    }
-
-    let code: Int
-    let data: T
-}
-
-struct NestedPostsJson: Decodable {
-    enum CodingKeys: String, CodingKey {
-        case code
-        case data
-
-        enum PostKeys: String, CodingKey {
-            case posts
-        }
-    }
-
-    init(from decoder: Decoder) throws {
-        let container = try decoder.container(keyedBy: CodingKeys.self)
-        let postsContainer = try container.nestedContainer(keyedBy: CodingKeys.PostKeys.self, forKey: .data)
-        data = try postsContainer.decode([WFPost].self, forKey: .posts)
-    }
-
-    let data: [WFPost]
-}
-
 public class WFClient {
     let decoder = JSONDecoder()