Create a SQL database on a Service

**Tell us about your request**
I would like to be able to attach an SQL database to my App Runner service from within the App Runner interface / YAML / API, and automatically gain private connectivity to this database from my service.

**Describe alternatives you've considered**
I could use Copilot for this, or I could use CDK - but those involve a lot of steep learning curves.

**Additional context**
When creating a microservice, the database should be encapsulated within that service - and not exist outside of it.