Support for multiple instances of a cdk.App

[BDQ]

The current definition of an environment for CDK seems to be an Account Id + Region pair, but what about a use case where we might want multiple instances of a single App in the same account / region?

In our use case, we want to have many separate staging/qa instances of a (multi-stack) cdk.App - and in some cases each App instance may include slight tweaks to the underlying CDK code.

As a workaround for now, I'm injecting the local branch name into the stack names for each app instance, as follows:

  const app = new cdk.App();

  const registryStack = new RegistryStack(app, `mp-${branchSafe}-ecr`);
  new BuildStack(app, `mp-${branchSafe}-bld` });

  app.run();

It'd be great to have official support for environment / instance labels to allow multiple copies of the same app in the same account/region. Bonus points if it could leverage tags.

[rix0rrr]

As a design note, I think a higher-level Construct that:

• Can contain Stacks.
• Can set an account/region that applies to all stacks in it.
• Participates in the generation of the stack names

Should be sufficient to achieve this. Then that containing construct can be instantiated multiple times.

[rix0rrr]

As an additional note about something that I missed last time around: App is designed to only be instantiated once. It's represents the "CDK App", not "your app".

[BDQ]

@rix0rrr - #1940 looks great! Thanks for this, it'll really help clean up my code!