Aurora-mysql rotation fix

[GNUKalashnikov]

Within this file: SecretsManagerRDSMySQLRotationSingleUser /lambda_function.py

I found a verfication check that only supports mysql. From my testing, I found that changing from aurora-mysql to just mysql creates a functional password rotation for the aurora-mysql db

Found on line 421:

    if 'engine' not in secret_dict or secret_dict['engine'] != 'mysql':
        raise KeyError("Database engine must be set to 'mysql' in order to use this rotation lambda")
    for field in required_fields:
        if field not in secret_dict:
            raise KeyError("%s key is missing from secret JSON" % field)

Propsed fix:

    if 'engine' not in secret_dict or (secret_dict['engine'] != 'mysql' and secret_dict['engine'] != 'aurora-mysql'):
        raise KeyError("Database engine must be set to 'mysql' in order to use this rotation lambda")
    for field in required_fields:
        if field not in secret_dict:
            raise KeyError("%s key is missing from secret JSON" % field)

This will allow for the verfication to pass aurora-mysql

[crus-umich]

Thank you for reaching out, we added the aurora engine types for the MySQL single user rotation lambda in the most recent PR.