AAP-43543 Force LDAP created usernames to be lowercase (ansible#714)

## Description
<!-- Mandatory: Provide a clear, concise description of the changes and
their purpose -->
- What is being changed?
Modify the LDAP authenticator to always use a lowercase username.

- Why is this change needed?
This is how it worked in 2.4, we accidentally overrode a function in the
2.5 implementation that broke this.

- How does this change address the issue?
This function was overridden in 2.5 and is responsible for converting
the username given to django into lowercase.

## Type of Change
<!-- Mandatory: Check one or more boxes that apply -->
- [X] Bug fix (non-breaking change which fixes an issue)
- [ ] New feature (non-breaking change which adds functionality)
- [ ] Breaking change (fix or feature that would cause existing
functionality to not work as expected)
- [ ] Documentation update
- [ ] Test update
- [ ] Refactoring (no functional changes)
- [ ] Development environment change
- [ ] Configuration change

## Self-Review Checklist
<!-- These items help ensure quality - they complement our automated CI
checks -->
- [X] I have performed a self-review of my code
- [X] I have added relevant comments to complex code sections
- [X] I have updated documentation where needed
- [X] I have considered the security impact of these changes
- [X] I have considered performance implications
- [X] I have thought about error handling and edge cases
- [X] I have tested the changes in my local environment

## Testing Instructions
<!-- Optional for test-only changes. Mandatory for all other changes -->
<!-- Must be detailed enough for reviewers to reproduce -->
### Prerequisites
<!-- List any specific setup required -->

### Steps to Test
1. With the new version of the authenticator attempt to login through
LDAP with usernames in different cases.
2. You should always have a lowercase username in django

### Expected Results
<!-- Describe what should happen after following the steps -->

## Additional Context
<!-- Optional but helpful information -->

### Required Actions
<!-- Check if changes require work in other areas -->
<!-- Remove section if no external actions needed -->
- [ ] Requires documentation updates
  <!-- API docs, feature docs, deployment guides -->
- [ ] Requires downstream repository changes
  <!-- Specify repos: django-ansible-base, eda-server, etc. -->
- [ ] Requires infrastructure/deployment changes
  <!-- CI/CD, installer updates, new services -->
- [ ] Requires coordination with other teams
  <!-- UI team, platform services, infrastructure -->
- [ ] Blocked by PR/MR: #XXX
  <!-- Reference blocking PRs/MRs with brief context -->

### Screenshots/Logs
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---------

Co-authored-by: Rick Elrod <[email protected]>

Author: john-westcott-iv

ansible_base/authentication/authenticator_plugins/ldap.py

@@ -180,6 +180,7 @@ def validate_ldap_filter(value: Any, with_user: bool = False) -> None:
     if with_user:
         if user_search_string not in value:
             raise ValidationError(_('DN must include "{}" placeholder for username: {}').format(user_search_string, value))
+
         dn_value = value.replace(user_search_string, 'USER')
 
     if re.match(r'^\([A-Za-z0-9-]+?=[^()]+?\)$', dn_value):
@@ -515,7 +516,7 @@ def get_or_build_user(self, username, ldap_user):
         This gets called by _LDAPUser to create the user in the database.
         """
         user, _authenticator_user, created = get_or_create_authenticator_user(
-            username,
+            username.lower(),
             self.database_instance,
             user_details={
                 "username": username,

test_app/tests/authentication/authenticator_plugins/test_ldap.py

@@ -1,3 +1,4 @@
+import importlib
 from collections import OrderedDict
 from unittest import mock
 from unittest.mock import MagicMock
@@ -679,3 +680,27 @@ def test_ldap_user_search_validation(
 )
 def test_ldap_search_field_is_single_search(value, expected_result):
     assert LDAPSearchField.is_single_search(value) is expected_result
+
+
+@pytest.mark.django_db
+@pytest.mark.parametrize(
+    "username",
+    [
+        ("Timmy"),
+        ("TIMMY"),
+        ("TiMmY"),
+    ],
+)
+def test_get_or_build_user(username, ldap_authenticator):
+    from ansible_base.authentication.authenticator_plugins import ldap
+
+    with mock.patch(
+        'ansible_base.authentication.utils.authentication.get_or_create_authenticator_user', return_value=(None, None, None)
+    ) as get_or_create_authenticator_user:
+        importlib.reload(ldap)
+        plugin = AuthenticatorPlugin(database_instance=ldap_authenticator)
+        ldap_object = MagicMock()
+        plugin.get_or_build_user(username, ldap_object)
+        assert get_or_create_authenticator_user.called
+        assert username.lower() in get_or_create_authenticator_user.call_args[0]
+        assert username not in get_or_create_authenticator_user.call_args[0]