Support ComposeContainer and DockerComposeContainer in Testcontainers integration

I'd like to define a new ConnectionDetails type for https://github.com/eclipse/kapua .
Eclipse Kapua can only be run via Docker compose. To achieve that, I run it successfully via org.testcontainers.containers.DockerComposeContainer.

I added a KapuaConnectionDetails:

public interface KapuaConnectionDetails extends ConnectionDetails {

  String baseHttpUrl();
}

I would have expected to be able to plug DockerComposeContainer as source of ContainerConnectionDetailsFactory.

But the current signature of ContainerConnectionDetailsFactory is:

public abstract class ContainerConnectionDetailsFactory<C extends Container<?>, D extends ConnectionDetails>
		implements ConnectionDetailsFactory<ContainerConnectionSource<C>, D> {}

Because of that, C excludes org.testcontainers.containers.DockerComposeContainer.

By looking at ContainerConnectionDetailsFactory, I didn't find a good reason for why C is restricted to Container<?>. ContainerConnectionDetailsFactory and its dependencies do not use Container<?>'s method. The only used method is from Startable, and it is only used after a cast check:

https://github.com/spring-projects/spring-boot/blob/c6619dd306b844ad7f876a9a7abc3661cc343dd1/spring-boot-project/spring-boot-testcontainers/src/main/java/org/springframework/boot/testcontainers/service/connection/ContainerConnectionDetailsFactory.java#L190-L192

Could we relax C restriction to allow DockerComposeContainer usage?

Start in spring-boot-project/spring-boot-testcontainers/src/main/java/org/springframework/boot/testcontainers/service/connection/ContainerConnectionDetailsFactory.java, especially the cast check around lines 190–192. Trace the generic type through its dependencies and assess support for DockerComposeContainer and ComposeContainer; done means both can serve as sources for a ContainerConnectionDetailsFactory without breaking existing container support.