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, 5 insertions, 0 deletions

diff --git a/pydis_site/apps/api/models/bot/nomination.py b/pydis_site/apps/api/models/bot/nomination.py
index 8a8f4d36..cd9951aa 100644
--- a/pydis_site/apps/api/models/bot/nomination.py
+++ b/pydis_site/apps/api/models/bot/nomination.py
@@ -39,3 +39,8 @@ class Nomination(ModelReprMixin, models.Model):
         help_text="When the nomination was ended.",
         null=True
     )
+
+    def __str__(self):
+        """Representation that makes the target and state of the nomination immediately evident."""
+        status = "active" if self.active else "ended"
+        return f"Nomination of {self.user} ({status})"