fix(self-hosted): grant supabase_functions_admin USAGE on extensions schema (#46526)

docker/volumes/db/webhooks.sql

@@ -122,6 +122,10 @@ BEGIN;
   ALTER table "supabase_functions".hooks OWNER TO supabase_functions_admin;
   ALTER function "supabase_functions".http_request() OWNER TO supabase_functions_admin;
   GRANT supabase_functions_admin TO postgres;
+  -- http_request() is SECURITY DEFINER and runs as supabase_functions_admin. Serializing
+  -- NEW/OLD can touch objects in the extensions schema (PostGIS geometry reads
+  -- extensions.spatial_ref_sys), so the role needs USAGE on it.
+  GRANT USAGE ON SCHEMA extensions TO supabase_functions_admin;
   -- Remove unused supabase_pg_net_admin role
   DO
   $$