🐛(back) allow ASCII characters in user sub field

All ASCII characters are allowed in a sub, we change the sub validator
to reflect this.

src/backend/core/tests/documents/test_api_documents_create_for_owner.py

@@ -148,7 +148,7 @@ def test_api_documents_create_for_owner_invalid_sub():
     data = {
         "title": "My Document",
         "content": "Document content",
-        "sub": "123!!",
+        "sub": "invalid süb",
         "email": "john.doe@example.com",
     }
 
@@ -163,10 +163,7 @@ def test_api_documents_create_for_owner_invalid_sub():
     assert not Document.objects.exists()
 
     assert response.json() == {
-        "sub": [
-            "Enter a valid sub. This value may contain only letters, "
-            "numbers, and @/./+/-/_/: characters."
-        ]
+        "sub": ["Enter a valid sub. This value should be ASCII only."]
     }
 
 

src/backend/core/tests/test_models_users.py

@@ -44,3 +44,25 @@ def test_models_users_send_mail_main_missing():
         user.email_user("my subject", "my message")
 
     assert str(excinfo.value) == "User has no email address."
+
+
+@pytest.mark.parametrize(
+    "sub,is_valid",
+    [
+        ("valid_sub.@+-:=/", True),
+        ("invalid süb", False),
+        (12345, True),
+    ],
+)
+def test_models_users_sub_validator(sub, is_valid):
+    """The "sub" field should be validated."""
+    user = factories.UserFactory()
+    user.sub = sub
+    if is_valid:
+        user.full_clean()
+    else:
+        with pytest.raises(
+            ValidationError,
+            match=("Enter a valid sub. This value should be ASCII only."),
+        ):
+            user.full_clean()