feat(rds): add ability to specify PreferredMaintenanceWindow to RDS cluster database instances

[rjjaisim-at-amazon]

Issue # (if applicable)

Closes #16954

Reason for this change

Noticed that we were able to specify preferredMaintenanceWindow for a cluster, but unable to do so for the instances created under the cluster. Instead, AWS (semi-)randomly assigns a maintenance window (doc) for the instances, which leads to things being out of sync b/w the cluster and its child instances

There are some workarounds as mentioned in the issue above, but those are a little hacky (imo) and I figured adding the preferredMaintenanceWindow as an instance prop is a better long-term solution. Also, it might be hard for other developers to find the workarounds as they are only mentioned in the above issue and aren't available through normal channels (Stack overflow/official CDK docs)

Description of changes

Added optional preferredMaintenanceWindow field under InstanceProps, and passed that field in during the creation of the CfnDBInstance. Also added a quick unit test

Description of how you validated changes

Added a unit test, did not add integ tests. Ran yarn build and yarn test

Callout: I was unable to run integration tests locally, kept getting errors with yarn integ --directory packages/aws-cdk-lib/aws-rds and yarn integ-runner --directory packages/aws-cdk-lib/aws-rds - Error: Cannot find module './integ-runner.js', not sure if I'm missing something

Checklist

• [ x ] My code adheres to the CONTRIBUTING GUIDE and DESIGN GUIDELINES

No breaking changes

By submitting this pull request, I confirm that my contribution is made under the terms of the Apache-2.0 license

[aws-cdk-automation]

The pull request linter has failed. See the aws-cdk-automation comment below for failure reasons. If you believe this pull request should receive an exemption, please comment and provide a justification.

A comment requesting an exemption should contain the text Exemption Request. Additionally, if clarification is needed add Clarification Request to a comment.

[rjjaisim-at-amazon]

Exemption Request: This is a small change, so I figured integration tests weren't necessary (there are also no integration tests for the other props). Likewise for the README.md requirement, as far as I can tell, there is no README that documents every single prop in a table that I could easily append this new prop to. IMO, addtition to README.md should be done as part of a larger chore and is out of scope for this.

Please let me know your thoughts

[xazhao]

I'm okay with no integration changes. But IMO we should add this property to README to give customers a better idea how to use it. We can add a small section specify preferred maintenance window and provide a simple example.

✅ Updated pull request passes all PRLinter validations. Dismissing previous PRLinter review.

[rjjaisim-at-amazon]

Added details to README.md.

As for validation of the string, I believe that is done at runtime when the stacks are deployed. This has always been the case for CfnDBInstances - the preferredMaintenanceWindow prop has always existed for CfnDBInstances, but has always been set to undefined when these instances were created under a cluster (and therefore AWS would semi-randomly set a value for it on creation). My PR only allows the ability to pass in preferredMaintenanceWindow prop when creating CfnDBInstances under a cluster instead of it being undefined. We should keep the validation as is IMO and it doesn't fall under the purview of my PR

[xazhao]

Looks good to me

Pull request has been modified.

[aws-cdk-automation]

AWS CodeBuild CI Report

• CodeBuild project: AutoBuildv2Project1C6BFA3F-wQm2hXv2jqQv
• Commit ID: cd77a28
• Result: SUCCEEDED
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[Konosh93]

@rjjaisim-at-amazon Thank you for this fix. I was wondering why this change utilized instanceProps and not writer and readers props instead, given that instanceProps is deprecated?
I tried to fix this in a new PR:

• feat(rds): specify PreferredMaintenanceWindow in reader or writer props #29686

[rjjaisim-at-amazon]

@Konosh93 Thanks for pointing that out, I wasn't aware of the writer and reader props - thanks for adding it