refactor: the API's serializers and the new VM form no longer need models

Networks, Interfaces, Storages, Storage, Volume, MigrateInstance and
CreateInstance were unmanaged models with no table, there only so that
ModelSerializers and the new VM ModelForm could take their fields. They
made content types and migrations, and their DO_NOTHING foreign keys
added reverse accessors that meant nothing (Compute.host,
Compute.target_host, Instance.source_host).

The serializers are plain Serializers and NewVMForm a Form, field for
field as the models gave them (types, lengths, required, defaults, the
minimum of 1 for vCPUs, memory and disk size; the form's labels are
still derived from the field names). Compared field by field before and
after, the API schema changes only where the models were wrong:
- no int64 bounds on the listing fields;
- the interface fields lose the titles that named the wrong column
  (type was "Status", state "Device", mac "Forward");
- a pool's volumes is a list of objects (it was described as an
  integer) and a volume's allocation an integer (it was untyped).
One migration per app deletes the models; none touches a table.

instances/forms.py

@@ -4,7 +4,7 @@ from django import forms
 from django.conf import settings
 from django.utils.translation import gettext_lazy as _
 
-from .models import CreateInstance, Flavor
+from .models import Flavor
 from .utils import nic_macs
 
 
@@ -100,30 +100,36 @@ class ConsoleForm(forms.Form):
         return data
 
 
-class NewVMForm(forms.ModelForm):
-    # name = forms.CharField(error_messages={'required': _('No Virtual Machine name has been entered')}, max_length=64)
-    # firmware = forms.CharField(max_length=50, required=False)
-    # vcpu = forms.IntegerField(error_messages={'required': _('No VCPU has been entered')})
-    # disk = forms.IntegerField(required=False)
-    # memory = forms.IntegerField(error_messages={'required': _('No RAM size has been entered')})
-    # networks = forms.CharField(error_messages={'required': _('No Network pool has been choosen')})
-    # nwfilter = forms.CharField(required=False)
-    # storage = forms.CharField(max_length=20, required=False)
-    # template = forms.CharField(required=False)
-    # images = forms.CharField(required=False)
-    # cache_mode = forms.CharField(error_messages={'required': _('Please select HDD cache mode')})
-    # hdd_size = forms.IntegerField(required=False)
-    # meta_prealloc = forms.BooleanField(required=False)
-    # virtio = forms.BooleanField(required=False)
-    # qemu_ga = forms.BooleanField(required=False)
-    # mac = forms.CharField(required=False)
-    # graphics = forms.CharField(error_messages={'required': _('Please select a graphics type')})
-    # video = forms.CharField(error_messages={'required': _('Please select a video driver')})
-    # listener_addr = forms.ChoiceField(required=True, widget=forms.RadioSelect, choices=QEMU_CONSOLE_LISTENER_ADDRESSES)
-    class Meta:
-        model = CreateInstance
-        fields = "__all__"
-        exclude = ["compute"]
+class NewVMForm(forms.Form):
+    """The new VM form (create_instance_w2.html); the API takes CreateInstanceSerializer."""
+
+    name = forms.CharField(max_length=64)
+    firmware = forms.CharField(max_length=64)
+    # an emulated TPM 2.0, as Windows 11 needs
+    tpm = forms.BooleanField(required=False)
+    vcpu = forms.IntegerField(min_value=1)
+    # a mode of libvirt's (host-model, host-passthrough, maximum) or a CPU model's name
+    vcpu_mode = forms.CharField(max_length=64)
+    disk = forms.IntegerField(required=False)
+    memory = forms.IntegerField(min_value=1)
+    networks = forms.CharField(max_length=256)
+    nwfilter = forms.CharField(max_length=256, required=False)
+    net_model = forms.CharField(max_length=256, required=False)
+    storage = forms.CharField(max_length=256, required=False)
+    template = forms.CharField(max_length=256, required=False)
+    images = forms.CharField(max_length=256, required=False)
+    cache_mode = forms.CharField(max_length=16)
+    hdd_size = forms.IntegerField(min_value=1, required=False)
+    meta_prealloc = forms.BooleanField(required=False)
+    virtio = forms.BooleanField(required=False, initial=True)
+    qemu_ga = forms.BooleanField(required=False)
+    mac = forms.CharField(max_length=255, required=False)  # one per NIC, comma separated
+    add_cdrom = forms.CharField(max_length=16)
+    # a NoCloud seed on a CD-ROM: the hostname and the creating user's SSH keys
+    cloud_init = forms.BooleanField(required=False)
+    add_input = forms.CharField(max_length=16)
+    video = forms.CharField(max_length=16)
+    listener_addr = forms.ChoiceField(choices=settings.QEMU_CONSOLE_LISTENER_ADDRESSES)
 
     def clean_name(self):
         name = self.cleaned_data["name"]