I have seen your other post as well, where you are asking for somebody who can help you coding the DH.
That API document is years old and outdated, and to be honest, it was non-secure due to the http setup. Indeed they have changed it already to https.
For example of a working integration, I would use the Home Assistant integration which can be found here:
It is up to date and works with Home Assistant.
Otherwise I would contact Growatt itself to make an integration to SmartThings. They could use the CURB energy DH as an example for SmartThings. It is a quite similar use case.
(The only problem to build DHs and integrations of this sort of servers, that you never know what is the allowed rate limit to get data from it. Some PV inverter manufacturers have a total request limit of 300 requests per day to their servers. That would allow you to get the data every 5 minutes during a 24 hour period. But it is the total request allowed, so apps and other sources counts as well…)