I have not used the NetApp Manageability SDK extentesively but I just ran through the documentation and did not see anything in regards to creating new users. However, someone else may be able to point us in the right direction.
One alternative I can suggest is a Python script that I put together that automates the process of SSH'ing into a controller and entering a set of commands. You can find the relevant code on the DatacenterDudes GitHub repo. I purposely left the code generic as possible so you'll have to tweak it a bit for your sepcific use case. If you do decide to go this route and run into problems I'm more than willing to help add the relvant functionality to the code.
Even though they are under the 'perldoc' area they are just HTML files with the API calls and data types. Since they are under the perldoc area they're all represented at Perl calls, so for example the perl function nfs_exportfs_list_rules_2 just translates to the nfs-exportfs-list-rules-2 API call (sub - for _ etc..).