Shared Lambda authorizer

I am trying to create a custom Lambda authorizer that will be shared between a few different services/serverless stacks. If I understand the documentation here https://serverless.com/framework/docs/providers/aws/events/apigateway/#note-while-using-authorizers-with-shared-api-gateway, that means that I need to create a shared authorizer resource in a “common resources” service/serverless stack, and then refer to that shared authorizer from my other services. First of all: Is my understanding correct?

If my understanding is correct, my next question becomes: How do I do this? The documentation doesn’t provide a clear example for lambda authorizers, so here’s how I tried to customize it:

functions:
authorizerFunc:
handler: authorizer/authorizer.handler
runtime: nodejs8.10

resources:
Resources:
authorizer:
Type: AWS::ApiGateway::Authorizer
Properties:
AuthorizerResultTtlInSeconds: 0
Name: Authorizer
Type: REQUEST
AuthorizerUri: ???
RestApiId:
Fn::ImportValue: myRestApiId

I don’t understand what the syntax for AuthorizerUri is supposed to be. I’ve tried “Ref: authorizerFunc”, “Fn::GetAtt: [authorizerFunc, Arn]” etc. to no avail.

When I get the authorizerUri working, do I just add an Output for my authorizer resource, then Fn::ImportValue it from the services containing my API Lambdas?

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