[#41] Allow users to download the user/planting guide for a payment

- backend changes

backend/right_tree/api/migrations/0015_auto_20230306_1620.py

@@ -0,0 +1,40 @@
+# Generated by Django 3.2.17 on 2023-03-06 03:20
+
+from django.db import migrations, models
+import django.db.models.deletion
+import right_tree.api.models
+
+
+class Migration(migrations.Migration):
+
+    dependencies = [
+        ('api', '0014_address_export_questionnaire'),
+    ]
+
+    operations = [
+        migrations.CreateModel(
+            name='ActivationKeySet',
+            fields=[
+                ('id', models.BigAutoField(auto_created=True, primary_key=True, serialize=False, verbose_name='ID')),
+                ('creation_date', models.DateTimeField(auto_now_add=True)),
+                ('name', models.CharField(max_length=255, unique=True)),
+                ('size', models.PositiveSmallIntegerField()),
+                ('initial_activations', models.SmallIntegerField(default=1)),
+            ],
+        ),
+        migrations.CreateModel(
+            name='ActivationKey',
+            fields=[
+                ('id', models.BigAutoField(auto_created=True, primary_key=True, serialize=False, verbose_name='ID')),
+                ('key', models.CharField(default=right_tree.api.models.ActivationKey.key_default, max_length=20, unique=True)),
+                ('remaining_activations', models.SmallIntegerField(default=1)),
+                ('creation_date', models.DateTimeField(auto_now_add=True)),
+                ('key_set', models.ForeignKey(null=True, on_delete=django.db.models.deletion.CASCADE, to='api.activationkeyset')),
+            ],
+        ),
+        migrations.AddField(
+            model_name='questionnaire',
+            name='key',
+            field=models.ForeignKey(null=True, on_delete=django.db.models.deletion.PROTECT, to='api.activationkey'),
+        ),
+    ]