Bug: Mobius Forms Attachments break because of System.Text.Json changes

[iJungleboy]

I'm submitting a ...
[x] bug report => search github for a similar issue before submitting

...about
[x] APIs like REST

Current behavior

Until recently we used Newtonsoft to handle WebAPI serialization #2916

But the change causes a problem with the existing Mobius App, which expects data in the JSON to be of a Newtonsoft type.

So we must ensure that all custom APIs created before can still Newtonsoft in DNN.

Your environment

• 2sxc version(s): 14.11