Disable create function ability

[wvangeit]

Since it was decided yesterday that we will only provide read-only function collections for the release, apart for certain users who would actively ask for it, we ideally have a mechanism to disable the 'creation' of function (not the entire function api).

Api server create function endpoint will have access rights for the endpoints.

[wvangeit]

Removing release label since the POs decide this is not a necessity.