Follow-up from "WIP: Feature/us0017"

The following discussion from !6 (merged) should be addressed:

• @quincy started a discussion:

  Besproken met Ryan, voor in de toekomst kan deze endpoint weg en vervangen worden met de endpoint LEARN_URL

• LTI does not confirm the authenticity of the LTI request.

• LTI does not activate an (expired) token

• LTI does not make use of the refresh token