Ensure that raster_columns is always readable by public unless explicitly made unreadable

[robe]

This is related to #2821. Some how strk got himself into a state where raster_columns is not readable by all users of a db, and thus raster import failed.

We currently have raster_columns as publically readable in the rtpostgis.sql.in

via

GRANT SELECT ON TABLE raster_columns TO public;
GRANT SELECT ON TABLE raster_overviews TO public;

Looking at my views, these lines DO show on permissions of these views. If a database were to be restored then CREATE EXTENSION would run which would reapply these permissions. Said permissions should also be included in upgrade. Perhaps they are not -- we need to confirm they are.

[strk]

Grants are not found in upgrade scripts:

$ grep -i GRANT raster/rt_pg/rtpostgis_upgrade.sql # no hits

[strk]

Nor in the extension upgrade scripts (derived from the former)

$ grep -iw GRANT extensions/postgis/sql/postgis--*--*.sql # no hits

I'm afraid we cannot really tell if the user explicitly made them unreadable.

Generally speaking, GRANTS have been usually left out of postgis enabler scripts, this is all a new thing. Maybe we should have a function to "reset to default permissions"

[strk]

Another idea would be that some function is made available to check the state of installation. Right now only "postgis_full_version" does some of that, warning if you're out of sync between library and scripts, maybe the same function could also check permissions and warn you about that ?

[strk]

See also #2823 which is about loosing all GRANTS on upgrade (either granted by system install or manually). Actually, maybe this is a duplicate. Your call, Regina.

[robe]

yah I think its a duplicate