Update: we agreed in delivery circle that it makes sense for @apb to look at the spike to balance his current work on the Rails 5.2 upgrade and s2 fighting.
To do the spike, we agreed with @apb that we would move forward step by step.
First step has been done by @apb this week by documenting our current authentifications methods up here: Authentication · openfoodfoundation/openfoodnetwork Wiki · GitHub
Next step is to explore Doorkeeper. Stay tuned.