Correctly query for parent on service, not for system.

[andrewstillv15]

Resolves #

Problem

I think this fully resolves the underlying cause of OpsLevel/terraform-provider-opslevel#617, unless I've misunderstood the issue. Manual testing I performed below.

Solution

Claude code wrote this lovely emoji filled manual test for me to validate the changes.

func ServiceSystemTest(client *opslevel.Client) {
	fmt.Println("=== Testing service.GetSystem() ===")

	// Find a service with a parent system
	services, err := client.ListServices(nil)
	if err != nil {
		fmt.Printf("❌ Failed to list services: %v\n", err)
		return
	}

	if len(services.Nodes) == 0 {
		fmt.Println("❌ No services found")
		return
	}

	var testService *opslevel.Service
	for _, svc := range services.Nodes {
		if svc.Parent != nil {
			testService = &svc
			fmt.Printf("Found service with parent system:\n")
			fmt.Printf("  Service ID: %s\n", svc.Id)
			fmt.Printf("  Service Name: %s\n", svc.Name)
			fmt.Printf("  Parent System ID (from service.Parent): %s\n\n", svc.Parent.Id)
			break
		}
	}

	if testService == nil {
		fmt.Println("❌ No services found with a parent system")
		return
	}

	// Test GetSystem() - queries the 'parent' field to get full System data
	fmt.Println("Calling service.GetSystem() to fetch full system details...")
	system, err := testService.GetSystem(client, nil)
	if err != nil {
		fmt.Printf("❌ GetSystem() FAILED: %v\n", err)
		return
	}

	if system == nil {
		fmt.Println("❌ GetSystem() returned nil (no error but no system)")
		return
	}

	// Success! Display all the system fields we retrieved
	fmt.Printf("\n✅ GetSystem() SUCCEEDED! Full system data retrieved:\n")
	fmt.Printf("  System ID: %s\n", system.Id)
	fmt.Printf("  System Name: %s\n", system.Name)
	fmt.Printf("  System Description: %s\n", system.Description)
	fmt.Printf("  System Aliases: %v\n", system.Aliases)
	if system.Owner.OnTeam.Id != "" {
		fmt.Printf("  System Owner: Team %s (ID: %s)\n", system.Owner.OnTeam.Alias, system.Owner.OnTeam.Id)
	}
	fmt.Printf("\n✅ Test passed: service.GetSystem() correctly queries 'parent' field\n")
}

Checklist

• I have run this code, and it appears to resolve the stated issue.
• This PR does not reduce total test coverage
• This PR has no user interface changes or has already received approval from product management to change the interface.
• Does this change require a Terraform schema change?
  • If so what is the ticket or PR #
• Make a changie entry that explains the customer facing outcome of this change