fix: make machine VMHost pointer

[skatsaounis]

• Turn the VMHost machine field to a pointer to differentiate machines backed by a VM host (VMs) and physical machines.
• Declare an internal MachineVMHost since only 3 fields of the machine's VM host are included in the response of the API link

Resolves: #27

[SK1Y101]

Looks good, but I wonder if the tests need changing, or are they fine?

[skatsaounis]

The tests are fine, but they are not capturing changes like this. What you can do to test it currently, is to use a dev MAAS and pick a real machine and a VM.

Tester go:

vm, err := client.Machine.Get("whhhdw")
if err != nil {
	fmt.Println(err)
}
fmt.Println(vm.VMHost.Name)

machine, err := client.Machine.Get("cwgwwh")
if err != nil {
	fmt.Println(err)
}
fmt.Println(machine.VMHost.Name)

Before the change:

$ go run main.go
1
0

After the change:

$ go run main.go
1
panic: runtime error: invalid memory address or nil pointer dereference
[signal SIGSEGV: segmentation violation code=0x1 addr=0x180 pc=0x6a7a54]

goroutine 1 [running]:
main.main()
	/home/skatsaounis/projects/go-playground/maasclient/main.go:264 +0x174
exit status 2

Which is fine since in order to fill it the machine should have a VM Host or pod

[SK1Y101]

Awesome!