Describe the bug
When a user signs in using Auth.signIn() the "signIn" event is registered multiple times in the Hub listener

To Reproduce

1. Add a log inside the "signIn" event in the Hub.listener callback
2. Open devtools
3. Sign in using Auth.signIn()
4. Notice there is at least 4 or more logs and the same amount of network calls

Expected behavior
The sign in event shou

I have the following setup:

• multiple stacks with shared API Gateway (see serverless docs)
• stack 1 defines a specific model and exports it (see serverless docs)
• stack 2 should make us of the model via Fn::ImportValue

Stack1:

custom:
  documentation:
    models:
      - name: BadRequest400ResponseJSON
        contentType: 'application/json'
        schema: ....