Avoid untyped methods

[manuwei]

Is your feature request related to a problem? Please describe.
Currently there are many untyped method throughout the project.

Describe the solution you'd like
Use OpenAPI to generate types and backend calls (these are typed) in the backend (this has already been setup for the quantil-ui call to patternatlas). This should make it easier to add typed backend calls as a developer. Document the necessary steps in our ReadTheDocs (this includes updating the generated files in the backend/frontend, use them in the frontend).

Describe alternatives you've considered
Enforcing typed methods with deepcode