new_contents: from django.db import migrations
  
  
  class Migration(migrations.Migration):
      """ Create a unique case-insensitive index on the username column """
  
      dependencies = [
          ('auth', '0001_initial'),
      ]
  
      operations = [
          migrations.RunSQL(
              'CREATE UNIQUE INDEX user_case_insensitive_unique '
              'ON auth_user ((lower(username)));',
              'DROP INDEX user_case_insensitive_unique',
          ),
      ]
  
subject: Add case-insensitive unique index for username