DatabaseCluster.clusterEndpoint.hostname does not respect LOCALSTACK_HOSTNAME

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When deploying my RDS stack I have it put it's hostname into an SSM Parameter to be used by Lambda functions later. This doesn't seem to work when configuring `LOCALSTACK_HOSTNAME`, `HOSTNAME` and `HOSTNAME_EXTERNAL`.

Given the following `docker-compose.yaml` and cdk files

```yaml
version: "3.5"
services:
localstack:
container_name: "localstack"
image: localstack/localstack:latest
network_mode: bridge
ports:
- "80:80"
- "443:443"
- "4566:4566"
- "4510-4559:4510-4559" # external services port range
- "127.0.0.1:53:53" # DNS config (only required for Pro)
- "127.0.0.1:53:53/udp" # DNS config (only required for Pro)
- "4571:4571"
environment:
- SERVICES=sqs, lambda, apigateway, s3, sts, ssm, cloudformation, ecr, kms, iam, rds
- LOCALSTACK_HOSTNAME=172.26.0.1
- HOSTNAME=172.26.0.1
- HOSTNAME_EXTERNAL=172.26.0.1
- DOCKER_HOST=unix:///var/run/docker.sock
- DEFAULT_REGION=eu-west-2
- TEST_AWS_ACCOUNT_ID=000000000000
volumes:
- "${TMPDIR:-/tmp/localstack}:/tmp/localstack"
- "/var/run/docker.sock:/var/run/docker.sock"
```

```ts
import { App, Stack } from "aws-cdk-lib";
import { Construct } from "constructs";
import { StringParameter } from "aws-cdk-lib/aws-ssm";
import {
AuroraPostgresEngineVersion,
DatabaseCluster,
DatabaseClusterEngine,
} from "aws-cdk-lib/aws-rds";
import { Vpc } from "aws-cdk-lib/aws-ec2";

class TestStack extends Stack {
constructor(scope: Construct, id: string) {
super(scope, id);

new DbConstruct(this, "consumer");
}
}

class DbConstruct extends Construct {
constructor(scope: Construct, id: string) {
super(scope, id);

const cluster = new DatabaseCluster(this, "DatabaseCluster", {
engine: DatabaseClusterEngine.auroraPostgres({
version: AuroraPostgresEngineVersion.VER_13_4,
}),
defaultDatabaseName: "database",
storageEncrypted: true,
instanceProps: {
vpc: new Vpc(this, "db-vpc"),
},
});

new StringParameter(this, `DatabaseEndpoint`, {
parameterName: "databaseEndpoint",
stringValue: cluster.clusterEndpoint.hostname,
});
}
}

const app = new App();

new TestStack(app, "stack");
```

I get the following results when querying by console

```
$ awslocal ssm get-parameter --name databaseEndpoint
{
"Parameter": {
"Name": "databaseEndpoint",
"Type": "String",
"Value": "localhost",
"Version": 1,
"LastModifiedDate": "2022-08-03T15:36:53.410000+01:00",
"ARN": "arn:aws:ssm:eu-west-2:000000000000:parameter/databaseEndpoint",
"DataType": "text"
}
}

$ awslocal rds describe-db-clusters
{
"DBClusters": [
{
"AllocatedStorage": 1,
"DatabaseName": "database",
"DBClusterIdentifier": "dbc-63393c9f",
"DBClusterParameterGroup": "default.aurora-postgresql13",
"DBSubnetGroup": "consumerDatabaseClusterSubnets68C9D7B3-baf5d77a",
"Status": "error",
"Endpoint": "172.26.0.1:4511",
"MultiAZ": false,
"Engine": "aurora-postgresql",
"EngineVersion": "13.4",
"Port": 4511,
"MasterUsername": "postgres",
"StorageEncrypted": false,
"DBClusterArn": "arn:aws:rds:eu-west-2:000000000000:cluster:dbc-63393c9f",
"IAMDatabaseAuthenticationEnabled": false,
"CopyTagsToSnapshot": true
}
]
}

```

Of note here is that the endpoint from `describe-db-clusters` is `172.26.0.1:4511` whereas the value that gets stored in ssm is `localhost`

Start with the docker-compose.yaml environment settings and the CDK example using DatabaseCluster.clusterEndpoint.hostname, then trace how the endpoint is synthesized and exposed through the local AWS services. Compare the SSM value with the endpoint returned by rds describe-db-clusters. Done means the configured host is respected instead of being stored as localhost.

Written by the indexing model from the issue text.