The current LanguageConnectionContext keeps the user authorization identifier for an SQL session.
The lcc is shared context also for nested connections (opened from stored procedures).
So far, for roles, the current role has been stored in the lcc also. However, SQL requires that
authorization identifers be pushed on a "authorization stack" when calling a stored procedure, cf.
SQL 2003, vol 2, section 188.8.131.52 and 4.27.3 and 10.4 GR 5h and i.
This allows a caller to keep its current role after a call even if changed by the stored procedure.
This issue will implement the current role name part ("cell") of the authorization stack.
The authorization stack will be implemented as part of the SQL session context.
The patch will also implement the pushing of the current unqualified schema name part of
the SQL session context, cf. 10.4 GR 5a (