Make privilege check on GRANT more strict for schemas and virtual schemas

Detail name	Value
Changelog Number	23140
Type	Improvement
Status	Open

Background

Currently, the privilege check on grant does not distinguish between virtual schemas and normal schemas.
This allows to assign the REFRESH privilege to normal schemas.
It also allows to assign other privileges (e.g., INSERT) to virtual schemas.
Note that granting these privileges has no effect on the behavior of the schemas..

Improvement

The Exasol db throws an error if a user tries to GRANT a privilege to a schema or virtual schema that has no effect.

Changed behavior

The Exasol db throws an error if a user tries to GRANT a privilege to a schema or virtual schema that has no effect.