[WIP] Feature/api v3 base

https://www.openproject.org/work_packages/8769
I'm not a big fan of `#try`. Why not use delegation here?

```ruby
delegate :name, to: :type, prefix: 'type', allow_nil: true
```


http://devblog.avdi.org/2011/06/28/do-or-do-not-there-is-no-try/