fix unit tests

sql/drop_tables.sql

@@ -82,6 +82,9 @@ DROP TABLE IF EXISTS public.schema_info CASCADE;
 -- a completely clean public schema if the extension were to be re-installed.
 -- It's generally safe to include these in a full reset script.
 
-DROP TABLE IF EXISTS public.spatial_ref_sys CASCADE;
-DROP TABLE IF EXISTS public.geometry_columns CASCADE;
-DROP TABLE IF EXISTS public.geography_columns CASCADE;
+-- These tables are owned by the 'postgis' extension and cannot be dropped directly.
+-- Doing so would require dropping the extension itself, which is not the goal of this script.
+-- We only want to reset the application's data, not the database's extensions.
+-- DROP TABLE IF EXISTS public.spatial_ref_sys CASCADE;
+-- DROP TABLE IF EXISTS public.geometry_columns CASCADE;
+-- DROP TABLE IF EXISTS public.geography_columns CASCADE;