[FIX] doc: building correctly autoclass references

doc/api_integration.rst

doc/howtos/backend.rst

doc/howtos/backend/exercise-access-rights

doc/howtos/backend/exercise-access-rules

doc/howtos/backend/exercise-basic-action

doc/howtos/backend/exercise-calendar

doc/howtos/backend/exercise-constraint-python

doc/howtos/backend/exercise-creation

doc/howtos/backend/exercise-dashboard

doc/howtos/backend/exercise-demo

doc/howtos/backend/exercise-domain-advanced

doc/howtos/backend/exercise-formview

doc/howtos/backend/exercise-model

doc/howtos/backend/exercise-model-inheritance

doc/howtos/backend/exercise-report

doc/howtos/backend/exercise-session

doc/howtos/backend/exercise-state-workflow

doc/howtos/backend/exercise-state-workflow-automatic

doc/howtos/backend/exercise-translations

doc/howtos/backend/exercise-wizard