What is the problem?

When creating a rds.DatabaseInstanceReadReplica, while it accepts domain and domain_role parameters, it does not accept an engine parameter.

Then deployment fails with

To use Domain, you must provide an eligible SQL Server, Oracle, or Postgres engines

Reproduction Steps

 vpc: ec2.Vpc

# source_instance: rds.DatabaseInstance

rds.DatabaseInstanceFromSnapshot(self, "Instance",
    snapshot_identifier="my-snapshot",
    engine=rds.DatabaseInstanceEngine.postgres(version=rds.PostgresEngineVersion.VER_12_3),
    vpc=vpc
)
instance = rds.DatabaseInstanceReadReplica(self, "ReadReplica",
    source_database_instance=source_instance,
    instance_type=ec2.InstanceType.of(ec2.InstanceClass.BURSTABLE2, ec2.InstanceSize.LARGE),
    vpc=vpc,
    domain='my-domain',
    domain_role=my_domain_role
)
assert instance.engine is None

What did you expect to happen?

Initially, suspected it would inherit the engine from the referenced database; or at least be able to provide an engine

What actually happened?

Could not join the domain

To use Domain, you must provide an eligible SQL Server, Oracle, or Postgres engines

CDK CLI Version

2.9.0

Framework Version

No response

Node.js Version

14.15.1

OS

Ubuntu 18

Language

Python

Language Version

3.7

Other information

No response