Addons data is not part of the Server model

[Szymongib]

Server struct does not have a Software field that is returned in the server response. This field contains Addons which includes additional server configuration such as disks or extra bandwidth.

Since this is not documented as part of the official API, I am not sure if it can be considered as such but I did not find any other way to fetch Addons data for servers.

I have included the desired change in our fork, if that is of interest to you and it can be considered as part of API, I can submit it as a patch.
ChorusOne@048355a