Get Arn or variables in Open API 3 file from serverless.yml

Hi all,

I would like to get the Arn (or separate variables to build the Arn) for my Lambda functions into my Open API 3.

This is the resource section from my serverless.yml:

      Type: "AWS::ApiGateway::RestApi"
        Name: my-function-name-${self:provider.stage}
        Body: ${file(./api.yaml)}

The x-amazon-apigateway-integration block:

        uri: # Someway to get entire arn?
          Fn::Join: [
                "eu-west-2", # Replace with region variable
                "eu-west-2", # Replace with region variable
                "123456789", # Replace with account id variable
                my-function-name", # Replace with function name
            statusCode: "200"
        passthroughBehavior: "when_no_match"
        httpMethod: "POST"
        contentHandling: "CONVERT_TO_TEXT"
        type: "aws_proxy"

I’m not sure what do to here, various ways from my Google foo is not working and I am simply not understanding the way these two things talk. I know they transpile to a cloud formation file and that’s about it.

Any ideas? I feel like this is day 1 stuff and I need a push in the right direction.