RDS Clusters: Setting default values

[madereddy]

• Guidance on how to reproduce the issue. Ideally, this should be a
  small code sample that can be run immediately by the maintainers.
  Failing that, let us know what you're doing, how often it happens, what
  environment you're using, etc. Be thorough: it prevents us needing to ask
  further questions.

conn.create_db_cluster(
            DBClusterIdentifier=cluster_id,
            AllocatedStorage=10,
            Engine="postgres",
            DatabaseName="staging-postgres",
            StorageEncrypted=True,
            DeletionProtection=True,
            PubliclyAccessible=False,
            AutoMinorVersionUpgrade=False,
            BackupRetentionPeriod=1,
            BacktrackWindow=86400,
            IAMDatabaseAuthenticationEnabled=True
            MasterUsername="test",
            MasterUserPassword="password",
            EnableCloudwatchLogsExports=["audit", "error"],
            DBClusterParameterGroupName="test",
            Tags=[
                {"Key": "test", "Value": "test"},
            ],
        )

• Tell us what you expected to happen. When we run your example code,
  what are we expecting to happen? What does "success" look like for your
  code?

Return the values used during creation.

            BacktrackWindow=86400,
            IAMDatabaseAuthenticationEnabled=True

• Tell us what actually happens. It's not helpful for you to say "it
  doesn't work" or "it fails". Tell us how it fails: do you get an
  exception? A hang? How was the actual result different from your expected
  result?

Checking BacktrackWindow will return 0 and IAMDatabaseAuthenticationEnabled will return False

• Tell us what version of Moto you're using, and
  how you installed it. Tell us whether you're using standalone server
  mode or the Python mocks. If you are using the Python mocks, include the
  version of boto/boto3/botocore.

boto3: 1.34.109
moto: 5.0.8

If you do not provide all of these things, it will take us much longer to
fix your problem.

[rafcio19]

@bblommers I can look into this