Database migration on quotas/users foreign key

I replaced the user_id field (that was an integer) by a foreign key
using the same name.
Signed-off-by: Matthieu Berjon <matthieu.berjon@inria.fr>

django/poc/migrations/0002_auto_20180316_1321.py

+# -*- coding: utf-8 -*-
+# Generated by Django 1.11 on 2018-03-16 13:21
+from __future__ import unicode_literals
+
+from django.db import migrations, models
+import django.db.models.deletion
+
+
+class Migration(migrations.Migration):
+
+    dependencies = [
+        ('poc', '0001_initial'),
+    ]
+
+    operations = [
+        migrations.AlterField(
+            model_name='quotas',
+            name='user_id',
+            field=models.IntegerField(db_column='user_id'),
+        ),
+        migrations.RenameField(
+            model_name='quotas',
+            old_name='user_id',
+            new_name='user',
+        ),
+        migrations.AlterField(
+            model_name='quotas',
+            name='user',
+            field=models.ForeignKey(null=True, on_delete=django.db.models.deletion.CASCADE, to='poc.Users'),
+        ),
+    ]