SpringBoot When using Testcontainers at development time with @ServiceConnection on a @Bean method, describe when to use the name attribute and why

See https://github.com/spring-projects/spring-boot/pull/36064 and in particular https://github.com/spring-projects/spring-boot/pull/36064#issuecomment-1606237500 for background. When using Testcontainers at development time with @ServiceConnection on a @Bean method, there's an increased need to use the name attribute of @ServiceConnection as the container instance isn't available for us to call getDockerImageName() on it. We should document this, describing when to use the name attribute and explaining why it's necessary.