[invoices] Quantities can be non-integers

Signed-off-by: Yohann D'ANELLO <ynerant@crans.org>

apps/treasury/migrations/0003_auto_20210313_1235.py

@@ -0,0 +1,25 @@
+# Generated by Django 2.2.19 on 2021-03-13 11:35
+
+import django.core.validators
+from django.db import migrations, models
+import django.db.models.deletion
+
+
+class Migration(migrations.Migration):
+
+    dependencies = [
+        ('treasury', '0002_invoice_remove_png_extension'),
+    ]
+
+    operations = [
+        migrations.AlterField(
+            model_name='product',
+            name='quantity',
+            field=models.FloatField(validators=[django.core.validators.MinValueValidator(0)], verbose_name='Quantity'),
+        ),
+        migrations.AlterField(
+            model_name='specialtransactionproxy',
+            name='remittance',
+            field=models.ForeignKey(null=True, on_delete=django.db.models.deletion.PROTECT, related_name='transaction_proxies', to='treasury.Remittance', verbose_name='Remittance'),
+        ),
+    ]

apps/treasury/models.py

@@ -5,6 +5,7 @@ from datetime import date
 
 from django.contrib.auth.models import User
 from django.core.exceptions import ValidationError
+from django.core.validators import MinValueValidator
 from django.db import models, transaction
 from django.db.models import Q
 from django.template.loader import render_to_string
@@ -131,12 +132,13 @@ class Product(models.Model):
         verbose_name=_("Designation"),
     )
 
-    quantity = models.PositiveIntegerField(
-        verbose_name=_("Quantity")
+    quantity = models.FloatField(
+        verbose_name=_("Quantity"),
+        validators=[MinValueValidator(0)],
     )
 
     amount = models.IntegerField(
-        verbose_name=_("Unit price")
+        verbose_name=_("Unit price"),
     )
 
     @property