GHSA-jc55-246c-r88f: SurrealDB has an Uncaught Exception Handling Nonexistent Role

Roles for system users are stored as generic Ident values and converted as strings and into the Role enum whenever IAM operations are to be performed that require processing the user roles. This conversion expects those identifiers to only contain the values owner, editor and viewer and will return an error otherwise. However, the unwrap() method would be called on this result when implementing std::convert::From<&Ident> for Role, which would result in a panic where a nonexistent role was used.