(toolkit-lib): Add programmatic API to get CDK bootstrap template

[JohannesKonings]

Describe the feature

Currently, @aws-cdk/toolkit-lib does not expose a programmatic interface to generate the CDK bootstrap template. Users must rely on the CLI command cdk bootstrap --show-template to obtain the CloudFormation template.

Use Case

Get the template and modificate it (e.g. add a log bucket for the asset bucket access logs) and bootstrap an environment in one typescript script

Proposed Solution

Somehow like this

const cdk = new Toolkit();
const bootstrapTemplate = await cdk.bootstrap.showTemplate();

Other Information

fallback to the cli

const resultCdkStandardTemplate = execSync('pnpm exec cdk bootstrap --show-template', {
    encoding: 'utf8',
  });

Acknowledgements

• I may be able to implement this feature request
• This feature might incur a breaking change

CDK version used

@aws-cdk/toolkit-lib@v1.12.2

Environment details (OS name and version, etc.)

linux