Add integration test suite for CORS requests
The [docs](https://www.apollographql.com/docs/apollo-server/security/cors#configuring-cors-options-for-apollo-server) mention that in v4 the user is responsible for setting up the CORS handler (and not the integration package). Nonetheless, it would be nice if there were integration tests that make sure that the recommended way is indeed working as intended.

For example, while developing https://github.com/apollo-server-integrations/apollo-server-integration-h3 I noticed that preflight requests shouldn't hit the apollo http handler (since it only accepts GET and POST). Thus, depending on the framework either the cors handler or the integration package should handle preflights. 

https://github.com/JabRef/JabRefOnline/blob/214c8b991827a2b71f6c0dd675a12280e8b874a9/server/e2e.test.ts#L44-L78 can serve as a very simple starting point. The usage could look as follows:
```ts
defineIntegrationTestSuite(
  async (
    serverOptions: ApolloServerOptions<BaseContext>,
    testOptions?: CreateServerForIntegrationTestsOptions
  ) => {

    // the usual stuff, setting up the apollo server as well as the app

    if (testOptions.corsOptions) {
       // add cors handler (depends on the framework of course), something like
       app.use('/', cors(testOptions.corsOptions))
    }
}
```
