feat(activities,people): Allow people to attend activities

resolve #13

activities/migrations/0004_activity_attendance_list.py

@@ -0,0 +1,19 @@
+# Generated by Django 2.2.10 on 2020-02-19 15:20
+
+from django.db import migrations, models
+
+
+class Migration(migrations.Migration):
+
+    dependencies = [
+        ('people', '0005_user_one_person'),
+        ('activities', '0003_rename_activity_series_fk'),
+    ]
+
+    operations = [
+        migrations.AddField(
+            model_name='activity',
+            name='attendance_list',
+            field=models.ManyToManyField(related_name='activities', to='people.Person'),
+        ),
+    ]