Secret manager rotation expects credential key names to be constant

[rbrishabh]

Hey, in the SecretsManagerRDSMySQLRotationSingleUser/lambda_function.py we expect the field names to be:

 {
        'engine': <required: must be set to 'mysql'>,
        'host': <required: instance host name>,
        'username': <required: username>,
        'password': <required: password>,
        'dbname': <optional: database name>,
        'port': <optional: if not specified, default port 3306 will be used>
    }

In our case, we were using key names as 'rds.engine' etc for internal purposes. I would expect the field names to be configurable/dynamic. Can we look into this? Thank you for your consideration!