Resolve "RelatedObjectDoesNotExist at / User has no person."

Closes #149 (closed)

aleksis/core/decorators.py

 from typing import Callable
 
-from django.contrib.auth.decorators import user_passes_test
+from django.contrib.auth.decorators import login_required, user_passes_test
 
 
 def admin_required(function: Callable = None) -> Callable:
     actual_decorator = user_passes_test(lambda u: u.is_active and u.is_superuser)
     return actual_decorator(function)
+
+
+def person_required(function: Callable = None) -> Callable:
+    """ Requires a logged-in user which is linked to a person. """
+
+    actual_decorator = user_passes_test(lambda u: user.person is not None)
+    return actual_decorator(login_required(function))