[AAP-48878] Add email field to AuthenticatorUser (#754)

## Description
- What is being changed?
The AuthenticatorUser model is extended with the `email` field. This PR
is only to add the field, which will be populated by a later ticket-
https://issues.redhat.com/browse/AAP-48066.
- Why is this change needed?
This change is needed to associate AuthenticatorUsers directly with
their email address. This will make it easier to debug issues regarding
how users authenticate into the platform, since we will be able to tell
directly which email address their authenticatoruser is configured with.
When authenticating via multiple different authenticators, we will sign
the user into the AAP account associated with their email.
- How does this change address the issue?
This change addresses the issue by adding the email field to the
AuthenticatorUser table, which will be later populated by AAP-48066.

## Type of Change
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- [x] New feature (non-breaking change which adds functionality)

## Self-Review Checklist
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checks -->
- [ ] I have performed a self-review of my code
- [ ] I have added relevant comments to complex code sections
- [ ] I have updated documentation where needed
- [ ] I have considered the security impact of these changes
- [ ] I have considered performance implications
- [ ] I have thought about error handling and edge cases
- [ ] I have tested the changes in my local environment

## Testing Instructions
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### Prerequisites
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### Steps to Test
1. 
2. 
3. 

### Expected Results
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## Additional Context
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### Required Actions
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- [ ] Requires documentation updates
  <!-- API docs, feature docs, deployment guides -->
- [ ] Requires downstream repository changes
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- [ ] 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
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### Screenshots/Logs
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Author: zkayyali812

ansible_base/authentication/migrations/0018_authenticatoruser_email.py

@@ -0,0 +1,18 @@
+# Generated by Django 4.2.21 on 2025-07-09 12:02
+
+from django.db import migrations, models
+
+
+class Migration(migrations.Migration):
+
+    dependencies = [
+        ('dab_authentication', '0017_alter_authenticator_slug'),
+    ]
+
+    operations = [
+        migrations.AddField(
+            model_name='authenticatoruser',
+            name='email',
+            field=models.EmailField(blank=True, default=None, help_text='The e-mail associated with this authenticator user.', max_length=254, null=True),
+        ),
+    ]

ansible_base/authentication/models/authenticator_user.py

@@ -42,6 +42,7 @@ class AuthenticatorUser(AbstractUserSocialAuth, AbstractCommonModel):
         on_delete=models.CASCADE,
         help_text=_("The local DB user related to this authenticator user."),
     )
+    email = models.EmailField(default=None, null=True, blank=True, help_text=_("The e-mail associated with this authenticator user."))
     # TODO: set self.authenticated based on the provider that is passed to this method.
     # the provider should be the name of the Authenticator model instance
     claims = models.JSONField(