I'm not necessarily completely new to Casper; just having some issues with the mechanics of uploading a custom payload to a Configuration Profile.
Was wanting to disable "reopen windows at next login."
Found an example .plist on JAMF nation that does just what I want to do: disable "reopen windows on next login" for all AD users.
Copied the code to TextEdit.
Saved the file with the extension .mobileconfig
My Mac recognizes this file as a profile. If I double click it, it asks me if I want to install it. Furthermore, if I click "Show Profile," it gives me the exact key pair I want to manage. All good.
But when I try to upload it to the JSS, I get an error that says "file must be in .plist format." Uh. okay. It's XML. The documentation says upload xml data for custom payloads.
What gives? Here's a screenshot showing that the local Mac recognizes it as a custom profile. Why can't the JSS? What am I doing wrong? 
I don't understand why you can't just copy the key pairs for the correct domain, etc. straight into the JSS. It's just text.
