CORS config on a per-path basis within a space

Because of recent [CloudEvent changes](https://github.com/serverless/event-gateway/pull/421) and [Subscription refactoring](https://github.com/serverless/event-gateway/pull/429), we need to allow users to set CORS configuration on a per-path basis within a space.