It works!

src/documents/models.py

@@ -0,0 +1,10 @@
+from django.db import models
+
+
+class Document(models.Model):
+
+    sender = models.CharField(max_length=128, blank=True, db_index=True)
+    title = models.CharField(max_length=128, blank=True, db_index=True)
+    content = models.TextField(db_index=True)
+    created = models.DateTimeField(auto_now_add=True)
+    modified = models.DateTimeField(auto_now=True)