Add test comments

packages/server/src/appMigrations/tests/migrations.spec.ts

@@ -3,6 +3,8 @@ import * as setup from "../../api/routes/tests/utilities"
 import { MIGRATIONS } from "../migrations"
 
 describe("migration", () => {
+  // These test is checking that each migration is "idempotent".
+  // We should be able to rerun any migration, with any rerun not modifiying anything. The code should be aware that the migration already ran
   it("each migration can rerun safely", async () => {
     const config = setup.getConfig()
     await config.init()