feat!: a VM's vmid is a string, and its config can describe its hardware

VMDict.vmid and VMConfigDict.vmid were int. Proxmox numbers its guests,
but VMware identifies a VM by UUID, which an int cannot hold. The
provisioning dicts already carried vmid as a string; the read side now
matches. Proxmox reports "100".

VMConfigDict gains optional hardware details -- os_name, cpu_type,
sockets, cores_per_socket, firmware, machine and passthrough (PCI/USB,
as VMPassthroughDict) -- so netOrk's VM hardware view can be filled by
any hypervisor instead of reading Proxmox's raw config through the
driver's private API.

Also fixes the README's hypervisor example, which still named the
pre-contract snapshot_create.

BREAKING CHANGE: VMDict.vmid and VMConfigDict.vmid are str.

tests/test_vm_identifiers.py

@@ -0,0 +1,53 @@
+"""A VM's ``vmid`` is a string on every hypervisor.
+
+Proxmox numbers its guests, but VMware identifies them by UUID or MoRef
+(``"vm-42"``). An ``int`` in the contract forced netOrk to call ``int()`` on
+whatever came back, which cannot represent the second kind at all. The
+provisioning dicts already carried ``vmid`` as a string; these pin the
+read-side dicts to the same type.
+"""
+
+from __future__ import annotations
+
+from typing import get_type_hints
+
+import pytest
+from napalm_device_types.models import (
+    VMConfigDict,
+    VMDict,
+    VMProvisionResultDict,
+)
+
+
+@pytest.mark.parametrize("model", [VMDict, VMConfigDict, VMProvisionResultDict])
+def test_vmid_is_a_string(model):
+    assert get_type_hints(model)["vmid"] is str
+
+
+class TestVMConfigCarriesWhatAHardwareViewShows:
+    """netOrk's VM hardware view used to read Proxmox's raw config through the
+    driver's private API. The contract has to carry those details so a second
+    hypervisor can fill the same view -- optionally, since not every platform
+    has every one of them."""
+
+    OPTIONAL = {
+        "os_name",
+        "cpu_type",
+        "sockets",
+        "cores_per_socket",
+        "firmware",
+        "machine",
+        "passthrough",
+    }
+
+    def test_hardware_details_are_optional_fields(self):
+        assert self.OPTIONAL <= VMConfigDict.__optional_keys__
+
+    def test_contract_core_stays_required(self):
+        assert "vmid" in VMConfigDict.__required_keys__
+        assert "disks" in VMConfigDict.__required_keys__
+
+    def test_passthrough_entry_shape(self):
+        from napalm_device_types.models import VMPassthroughDict
+
+        assert get_type_hints(VMPassthroughDict) == {"slot": str, "kind": str, "config": str}