Allow to select billing period when registering VM

uncloud/uncloud_vm/serializers.py

@@ -2,6 +2,7 @@ from django.contrib.auth import get_user_model
 
 from rest_framework import serializers
 from .models import VMHost, VMProduct, VMSnapshotProduct
+from uncloud_pay.models import RecurringPeriod
 
 class VMHostSerializer(serializers.HyperlinkedModelSerializer):
     class Meta:
@@ -10,10 +11,19 @@ class VMHostSerializer(serializers.HyperlinkedModelSerializer):
 
 
 class VMProductSerializer(serializers.HyperlinkedModelSerializer):
+    # TODO: move this to VMProduct.
+    allowed_recurring_periods=list(filter(
+        lambda pair: pair[0] in [RecurringPeriod.PER_MONTH, RecurringPeriod.PER_HOUR],
+        RecurringPeriod.choices))
+
+    # Custom field used at creation (= ordering) only.
+    recurring_period = serializers.ChoiceField(
+            choices=allowed_recurring_periods)
+
     class Meta:
         model = VMProduct
         fields = ['uuid', 'order', 'owner', 'status', 'name', \
-                'cores', 'ram_in_gb']
+                'cores', 'ram_in_gb', 'recurring_period']
         read_only_fields = ['uuid', 'order', 'owner', 'status']
 
 class VMSnapshotProductSerializer(serializers.ModelSerializer):