Authentication/Authorization: allow X-API-KEY?

[GeriWolters]

Kennis Platform API's appears to state in the recent specification that X-API-KEY is a valid method for authentication, but not for authorization.
This should allow for certain requests to be done by using API keys. This should ONLY be implemented for retrieving data, not for the optional functionalities as subscriptions or inserts/updates.

This would also make it easier to consume the OData services using Excel. For Excel, OData is not the problem, but authentication is.