feat(agreement): add agreement field to user model and implement agreement upload functionality ✨

api/models.py

@@ -34,6 +34,13 @@ class User(AbstractUser):
     island = models.ForeignKey(
         "Island", on_delete=models.SET_NULL, null=True, blank=True, related_name="users"
     )
+
+    agreement = models.FileField(
+        upload_to="agreements/",
+        blank=True,
+        null=True,
+        help_text="Upload the agreement file signed by the user.",
+    )
     created_at = models.DateTimeField(default=timezone.now)
     updated_at = models.DateTimeField(auto_now=True)