fix customslug test: use store receiver

customslug_test.go

@@ -60,11 +60,11 @@ func TestCustomSlugValidation(t *testing.T) {
 func TestSlugCollisionWithAutoID(t *testing.T) {
 	s := testServer(t)
 	// manually insert a paste, then try to claim its auto ID as a custom slug
-	p, err := s.CreatePaste(&Paste{Content: "auto"})
+	p, err := s.store.CreatePaste(&Paste{Content: "auto"})
 	if err != nil {
 		t.Fatal(err)
 	}
-	if taken, _ := s.SlugTaken(p.ID); !taken {
+	if taken, _ := s.store.SlugTaken(p.ID); !taken {
 		t.Fatal("auto id should be claimed")
 	}
 }