Migrate nominations to new Nomination model

Before the migration to Django, we stored meta data on a nomination,
such as the `reason` and `end_reason`, in the infraction table using
"note" infractions, using a special prefix for the `reason`.

We have since decided to move nominations out of the infraction
context by creating a special `Nomination` model. However, given the
complexity of the data migration, we did not yet migrate the old
nomination data to this new model. This commit migrates that data by performing a data migration.

The data migration works as follows:

- Query all nomination data in chronological order;

- Replay all nominations and add them to the `Nomination` model;

- Delete the now obsolete `Infraction` entry.

In addition, this commit also adds a useful string representation for
`Nomination` objects.

1 files changed, 31 insertions, 5 deletions

diff --git a/pydis_site/apps/api/tests/test_models.py b/pydis_site/apps/api/tests/test_models.py
index 2120b056..aaf12045 100644
--- a/pydis_site/apps/api/tests/test_models.py
+++ b/pydis_site/apps/api/tests/test_models.py
@@ -3,11 +3,18 @@ from datetime import datetime as dt, timezone
 from django.test import SimpleTestCase
 
 from ..models import (
-    DeletedMessage, DocumentationLink,
-    Infraction, Message,
-    MessageDeletionContext, ModelReprMixin,
-    OffTopicChannelName, Reminder,
-    Role, Tag, User
+    DeletedMessage,
+    DocumentationLink,
+    Infraction,
+    Message,
+    MessageDeletionContext,
+    ModelReprMixin,
+    Nomination,
+    OffTopicChannelName,
+    Reminder,
+    Role,
+    Tag,
+    User
 )
 
 
@@ -27,6 +34,19 @@ class ReprMixinTests(SimpleTestCase):
 
 class StringDunderMethodTests(SimpleTestCase):
     def setUp(self):
+        self.nomination = Nomination(
+            id=123,
+            actor=User(
+                id=9876, name='Mr. Hemlock',
+                discriminator=6666, avatar_hash=None
+            ),
+            user=User(
+                id=9876, name="Hemlock's Cat",
+                discriminator=7777, avatar_hash=None
+            ),
+            reason="He purrrrs like the best!",
+        )
+
         self.objects = (
             DeletedMessage(
                 id=45,
@@ -102,3 +122,9 @@ class StringDunderMethodTests(SimpleTestCase):
     def test_returns_string(self):
         for instance in self.objects:
             self.assertIsInstance(str(instance), str)
+
+    def test_nomination_str_representation(self):
+        self.assertEqual(
+            "Nomination of Hemlock's Cat#7777 (active)",
+            str(self.nomination)
+        )