DPA Update DB Instance Connection via Rest API

Hi There

I've gone through the swagger ui and tried to figure this out..but I'm at my wits end.  Basically, we want to update a connection's properties via the rest api...not unregister/re-regsiter...we are swapping host's for dbs and would like to keep all the history for the new & old server under one cname....

Basically...how can we get this ^^ functionality via the rest api?

Thank you for reading!