refactor: Make Person.discipline free text

See #33

people/migrations/0021_refactor_person_disciplines.py

@@ -0,0 +1,61 @@
+# Generated by Django 2.2.10 on 2020-06-24 14:19
+
+from django.db import migrations, models
+
+
+def migrate_forward(apps, schema_editor):
+    Person = apps.get_model('people', 'Person')
+
+    for person in Person.objects.all():
+        try:
+            person.disciplines = person.discipline.name
+            person.save()
+
+        except AttributeError:
+            pass
+
+
+def migrate_backward(apps, schema_editor):
+    Person = apps.get_model('people', 'Person')
+    Discipline = apps.get_model('people', 'Discipline')
+
+    for person in Person.objects.all():
+        try:
+            discipline_str = person.disciplines.split(',')[0]
+
+        except AttributeError:
+            pass
+
+        else:
+            # Returns None if not found - doesn't raise exception
+            discipline = Discipline.objects.filter(name=discipline_str).first()
+
+            if not discipline:
+                discipline = Discipline.objects.create(
+                    name=discipline_str,
+                    code=discipline_str
+                    if len(discipline_str) < 15 else discipline_str[:15])
+
+            person.discipline = discipline
+            person.save()
+
+
+class Migration(migrations.Migration):
+
+    dependencies = [
+        ('people', '0020_person_organisation_started_date'),
+    ]
+
+    operations = [
+        migrations.AddField(
+            model_name='person',
+            name='disciplines',
+            field=models.CharField(blank=True, max_length=255, null=True),
+        ),
+        migrations.RunPython(migrate_forward, migrate_backward),
+        migrations.RemoveField(
+            model_name='person',
+            name='discipline',
+        ),
+        migrations.DeleteModel(name='Discipline', ),
+    ]