Need to define apiKeySource for ApiGateway with custom authorizer


I would like to be able to provide the ability to have my customer authorizer be the source of the api key, as per the aws docs

Event though there is no reference to this setting in the serverless docs, I have tried setting the value in the global provider settings

        apiKeySource: AUTHORIZER

However the cloud formation template does not produce any result with this, which was kind of expected.

"ApiGatewayRestApi": {
    "Type": "AWS::ApiGateway::RestApi",
    "Properties": {
        "Name": "test-api-gateway-dev",
        "EndpointConfiguration": {
            "Types": [

This should be technically possible, I am wondering if there is any support for this? or if serverless enforces the use of the HEADER value which then requires the key to be provided int the x-api-key header.