Hey again,

I wanted to tackle #372 but it showed the following error:

It seems that after years of warnings the time of updating the client has come.

So I generated a new client version (including Java 11 instead of Java 7). It needed some adjustments (see new README instructions and updated gradle code), but it works now.

I've used the newest available version of Swagger Codegen.

What do you think? There shouldn't be breaking changes in the code itself, right?
I will test the new version some more, but for now everything seems to be working.