Init Authorizer with different settings based on stage

Is it possible to initialize an Authorizer (CognitoUserPoolAuthorizer) with a different set of settings based on the stage the application is deployed to?

E.g. when deploying to a "dev" stage, the following settings will be used:
`authorizer = CognitoUserPoolAuthorizer('dev-userpool', header='Authorization', provider_arns=['arn:aws.....dev...'])`

...while deploying to a "prod" stage, the following settings will be used:
`authorizer = CognitoUserPoolAuthorizer('prod-userpool', header='Authorization', provider_arns=['arn:aws.....prod....'])`

I believe it is possible to do this with a batch-script which is run before calling the `chalice deploy --stage ` command, but it would have been great if this is part of the chalice framework, or could become a part of it in the future.

Start by reviewing how `chalice deploy --stage ` handles stage-specific configuration and how `CognitoUserPoolAuthorizer` settings are initialized. Done means authorizer settings can differ between the stated dev and prod deployment stages, with the behavior covered by appropriate project tests.

Written by the indexing model from the issue text.