Design Authz

[tmnd1991]

We need to define how we want to deal with authorization.
For sure access to tables is granted to the recipients of the share the table is part of.
More tricky is the part w/r/t admin part of the API. Right now we have an owner of various objects (providers, storage, metastores, internal tables) and as a first iteration we can let only that user modify/delete that objects.