Move the server code inside server dir

server/notes/models.py

@@ -0,0 +1,39 @@
+from django.contrib.auth.models import AbstractUser
+from django.db import models
+from django.utils import timezone
+
+# Create your models here.
+
+
+class User(AbstractUser):
+    allow_notes_from = models.ManyToManyField(
+        "User", related_name="allowed_notes_to", blank=True
+    )
+    expiry_seconds = models.PositiveIntegerField(default=86400)
+
+    @property
+    def alive_received_notes(self) -> models.QuerySet["Note"]:
+        return self.received_notes.filter(expiry__gt=timezone.now()).select_related(
+            "from_user", "to_user"
+        )
+
+    @property
+    def visible_name(self) -> str:
+        if self.first_name or self.last_name:
+            return self.get_full_name()
+        return self.username
+
+
+class Note(models.Model):
+    from_user = models.ForeignKey(
+        User, on_delete=models.CASCADE, related_name="created_notes"
+    )
+    to_user = models.ForeignKey(
+        User, on_delete=models.SET_NULL, null=True, related_name="received_notes"
+    )
+    note = models.TextField()
+    expiry = models.DateTimeField()
+    created_at = models.DateTimeField(auto_now_add=True)
+
+    def __str__(self):
+        return f"{self.from_user.username} -> {self.to_user.username}: {self.note[:30]}"