Move client code and test data generation methods to a new subproject

[subotic]

The routes are overcrowded now. There is more code for generating client code and test data then the actual route code itself.

related: #1501

[benjamingeer]

I find it easier to maintain the client function definitions if they’re in the routes rather than in a separate class, and since I’m the one who is maintaining them, I’d like to leave them that way. If you’d like to maintain them, you’re welcome to move them.