Add wallpaper samples price constraint (#322)

migrations/000.413.sql

@@ -0,0 +1,5 @@
+-- Remove duplicate check on wallpaper kit price
+ALTER TABLE prices_other_products DROP CONSTRAINT prices_other_products_wallpaper_kit_price_check1;
+
+-- Add check on on samples price
+ALTER TABLE prices_other_products ADD CONSTRAINT valid_samples_price CHECK (wallpaper_sample_price > 0);