oauth2: use auto_now_add for creation_date fields (#22682)

fargo/oauth2/migrations/0004_auto_20180326_1330.py

@@ -0,0 +1,25 @@
+# -*- coding: utf-8 -*-
+# Generated by Django 1.11.11 on 2018-03-26 13:30
+from __future__ import unicode_literals
+
+from django.db import migrations, models
+
+
+class Migration(migrations.Migration):
+
+    dependencies = [
+        ('oauth2', '0003_auto_20180322_1016'),
+    ]
+
+    operations = [
+        migrations.AlterField(
+            model_name='oauth2authorize',
+            name='creation_date',
+            field=models.DateTimeField(auto_now_add=True),
+        ),
+        migrations.AlterField(
+            model_name='oauth2tempfile',
+            name='creation_date',
+            field=models.DateTimeField(auto_now_add=True),
+        ),
+    ]

fargo/oauth2/models.py

@@ -68,7 +68,7 @@ class OAuth2Authorize(models.Model):
     user_document = models.ForeignKey(UserDocument)
     access_token = models.CharField(max_length=255, default=generate_uuid)
     code = models.CharField(max_length=255, default=generate_uuid)
-    creation_date = models.DateTimeField(auto_now=True)
+    creation_date = models.DateTimeField(auto_now_add=True)
 
     def __repr__(self):
         return 'OAuth2Authorize for document %r' % self.user_document
@@ -79,4 +79,4 @@ class OAuth2TempFile(models.Model):
     client = models.ForeignKey(OAuth2Client)
     document = models.ForeignKey(Document)
     filename = models.CharField(max_length=512)
-    creation_date = models.DateTimeField(auto_now=True)
+    creation_date = models.DateTimeField(auto_now_add=True)