Registers an Amazon RDS instance with a stack.
See https://paws-r.github.io/docs/opsworks/register_rds_db_instance.html for full documentation.
opsworks_register_rds_db_instance(
StackId,
RdsDbInstanceArn,
DbUser,
DbPassword
)[required] The stack ID.
[required] The Amazon RDS instance's ARN.
[required] The database's master user name.
[required] The database password.