AFN 请求头添加 utf-8识别

review by 枪老板

@@ -512,7 +512,7 @@ forHTTPHeaderField:(NSString *)field
             mutableRequest.URL = [NSURL URLWithString:[[mutableRequest.URL absoluteString] stringByAppendingFormat:mutableRequest.URL.query ? @"&%@" : @"?%@", query]];
         } else {
             if (![mutableRequest valueForHTTPHeaderField:@"Content-Type"]) {
-                [mutableRequest setValue:@"application/x-www-form-urlencoded" forHTTPHeaderField:@"Content-Type"];
+                [mutableRequest setValue:@"application/x-www-form-urlencoded; charset=utf-8" forHTTPHeaderField:@"Content-Type"];
             }
             [mutableRequest setHTTPBody:[query dataUsingEncoding:self.stringEncoding]];
             

@@ -235,7 +235,7 @@ NSDictionary *parameters = @{@"foo": @"bar", @"baz": @[@1, @2, @3]};
 ```
 
     POST http://example.com/
-    Content-Type: application/x-www-form-urlencoded
+    Content-Type: application/x-www-form-urlencoded; charset=utf-8
 
     foo=bar&baz[]=1&baz[]=2&baz[]=3