Review all internal errors

[glpatcern]

The current code base uses status.NewInternal() in far too many places as a "shortcut" to report an error. In many/most occurrences, a more tailored error code should be used for the caller to display proper error messages, and logging should be adapted as well.

Here follows the count per GRPC service:

applicationauth: 4
appregistry: 6
authregistry: 2
datatx: 4
gateway: 104
groupprovider: 5
ocmcore: 1
ocminvitemanager: 10
ocmproviderauthorizer: 3
ocmshareprovider: 12
preferences: 2
publicshareprovider: 6
publicstorageprovider: 9
storageprovider: 64
storageregistry: 3
userprovider: 4
usershareprovider: 8