(aws-appsync): rdsDataSource expects databaseCluster instead of serverlessCluster

Creating seperate issues for #12503 to improve strucure.

When trying to add a rdsDataSource to appsync, addRdsDataSource and RdsDataSource expects a DatabaseCluster instead of a ServerlessCluster, which is the one used by AppSync.

Reproduction Steps

const api = new GraphqlApi(stack, 'api', {
  name: 'graphqlApi',
  schema: Schema.fromAsset('./testSchema.graphql'),
});

const serverless = new ServerlessCluster(stack, 'cluster', {
  engine: DatabaseClusterEngine.AURORA_MYSQL,
  vpc: new Vpc(stack, 'vpc'),
});

api.addRdsDataSource('rdsDS', serverless, serverless.secret!);

What did you expect to happen?

addRdsDataSource to expect ServerlessCluster.

What actually happened?

It expects a DatabaseCluster.

Environment

• CDK CLI Version: 1.84.0
• Framework Version: 1.84.0
• Node.js Version: 14.5.4
• OS: MacOS 10.15.7
• Language (Version): TypeScript (3.9.7)

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This is 🐛 Bug Report

[Simon-TechForm]

Hello @MrArnoldPalmer

I appreciate you taking the time to get back to me on this. I will hit you up in the pr (and maybe #12575 as well? 😉 )

Have a nice weekend.

[Simon-TechForm]

Shamelessly going to mention a few people being the last ones active on this repo: @skinny85 @njlynch @rix0rrr

Could someone please shed some light on what to expect about appsync within this project?

I’m aware that the cdk contructs of appsync are marked as experimental, and as such might not be highly prioritized, but it has now been almost a month since we opened this issue (and #12572) with corresponding pr’s, and we haven’t heard a word from aws.

We are happily using aws-cdk and deemed it the favorable option for coding backend within aws, but we use appsync in a lot of our projects and therefore need to know if it has been left for dead in aws-cdk. Looking at the issues, there have been almost zero activity in 2021 regarding appsync.