Log enhancement for aclcheck permissions failures

Hi hackers,

I was wondering if we can improve the error messages for acl permission
failures.
Current implementation to report errors is in "backend/catalog/aclchk.c"
void aclcheck_error(AclResult aclerr, ObjectType objtype, const char
*objectname);

based on the AclResult type, it print log messages like
"permission denied for schema %s"
which tells the admins what could be the domain of the permission-deny,
like table name or schema name.

However, I find that the log messages *lack* more details, i.e., the
*exact permission* that causes the permission-deny. For the novice users,
they may end up over-granting the permission to fix the issues
and cause security vulnerability in the database.

I think the log messages can be better if we add some diagnostic
information like which *role* is denied and what *permission* it lacks.
This way the users know which permission to grant exactly
without the trial-and-errors.

It is not hard to improve the log messages after looking into the code.
Most places use the function aclcheck_error() exactly after the permission
check, e.g., pg_type_aclcheck(), pg_tablespace_aclcheck().
For example, in backend/commands/dbcommands.c, it checks whether
the user has CREATE permission.

aclresult = pg_tablespace_aclcheck(dst_deftablespace, GetUserId(),
ACL_CREATE);
if (aclresult != ACLCHECK_OK)
aclcheck_error(aclresult, OBJECT_TABLESPACE, tablespacename);

We can simply change the aclcheck_error() function parameter a bit,
then we can pass the exact permission to the function, and tell the users
exactly why the permission is denied. Something would be like

void aclcheck_error(AclResult aclerr, ObjectType objtype,
const char *objectname,
const char *privilegename)

Any thoughts would be appreciated. Thanks!

Best regards,
Bingyu