AWS AppSync Caching - Using header parameters as keys to configure caching calling graphql queries

Hi all and thanks in advance for your help, I need to implement a caching layer on AWS AppSync for my queries to graphql. I already used the context.arguments object to specify the keys for the caching like this:

  - dataSource: aws_appsync_lambda
    type: Query
    field: getProductSkusByCarouselUuid
    caching:
      ttl: 600
      keys:
        - '$context.arguments.carouselUuid'

but I also need to use a parameter set in the headers of the request.

Is there a way to specify header parameters in keys? Or am I obliged to pass the parameter as a query argument?

Thanks