regenerate stubs for v1.3, remove unused code

[dlebauer]

• [ ] reduce the openapi.yml to only provide the endpoints that we support
• [x] regenerate stubs
• [x] update README.md
  • document how to add new endpoints from the yml
• [x] get the API working again

[robkooper]

removed code to generate stubs, now is automagically.

[robkooper]

will close issue for now, we can cut down the brapi.yaml at a later time.