Copying a job using the /createItem?mode=copy API requires the use of a Content-Type HTTP header, which doesn't make sense for the 'copy' operation as the input data is being sourced internally and not being supplied in the HTTP request (there is no user-supplied 'content' whose type needs describing in this case).

At the time of this writing, omitting the Content-Type header results in an error message, forcing the user to supply any arbitrary Content-Type in order to allow the request to succeed.