EventRules cannot have targets with the same Construct ID.

[robwettach]

Describe the bug
Two Lambda Functions with the same Construct ID but in different scopes cannot both be used as targets to the same EventRule:

Error: Duplicate event rule target with ID: Resource
    at EventRule.addTarget (.../node_modules/@aws-cdk/aws-events/lib/rule.js:57:19)
    at new EventRule (.../node_modules/@aws-cdk/aws-events/lib/rule.js:26:18)

The issue is that Function's asEventRuleTarget uses node.id as the id field for the EventRuleTargetProps (source). This isn't unique, as it's just the ID that was passed when creating the Function construct - instead it should use node.uniqueId (source). This needs to be globally unique as when calling EventRule.addTarget this value is used as a unique identifier (source).

To Reproduce

class CustomConstruct extends Construct {
  public readonly lambda: Function;

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

    this.lambda = new Function(this, "Resource", {
      code: new InlineCode("def handler:\n\tprint(\"Hello\")"),
      handler: "index.handler",
      runtime: Runtime.Python36
    });
  }
}

const construct1 = new CustomConstruct(this, "Construct1");
const construct2 = new CustomConstruct(this, "Construct2");

new EventRule(this, "ConflictingRule", {
  description: "This will fail because the targets both have the same Construct ID",
  scheduleExpression: "rate(1 minute)",
  enabled: true,
  targets: [
    construct1.lambda,
    construct2.lambda
  ]
});

Expected behavior
I can name my constructs in any manner I want, they can still be accepted as distinct EventRule targets without collision between two distinct construct instances.

Version:

• OS: Mac OS
• Programming Language: TypeScript
• CDK Version: 0.26.0

[made2591]

The bug is still present in version 0.33: fixed in #2744