Fixed Security Issues

Fixed Security Issues in JsonPreviewController.

(CMS-21340)

Preserve Order in Maps Returned by Headless Server

Previously the order of maps from structs were not preserved in the Headless Server. This was due to a bug in the implementation of the {{MapToNestedMapsConverter }} which is now fixed. This affects all the maps retrieved from structs and the results of the MapOf* scalar types.

(CMS-21175)