getRequired and handle for an 1 entity.

Right now part of CoreCacheManager looks something like this:

public List<DTO> getAndHandleAll(List<ID> ids, Consumer<List<ID>> handleMissing) {}

public List<DTO> getAndHandle(List<ID> ids, Consumer<ID> handleMissing) {}

It would be nice to have something like

public DTO getOrHandleAndThrow(ID id, Consumer<ID> handleMissing) {}

so that we can deal with situations like this,

public class CapacitySession extends QueueSession<SelectionRequest> {

	...

	@Override
	public boolean allowsRequest(Request<?> request) {
		var session = getBean(SessionCacheManager.class).get(getSession()); // we soft delete the session here, and throw
                ...
        }
}

We can achieve cascading soft deletes without this, it just increases code quality.