Dependent params

Based on documentation one can use dependent params with the following

  optional :category
  given category: ->(val) { val == 'foo' } do
    requires :description
  end
end

where category in itself is a param however I would like something like the following

  given api_key: ->(val) { val == 'foo' } do
    requires :description
  end
end

where api_key is not a param but a header which is already parsed in the base api class and is available. Is this possible ?

Start with the dependent-params documentation and the base API class where the header is already parsed. Trace how given conditions access declared parameters, then determine whether the existing API supports using that header value. Done means the supported behavior is clearly documented and the conditional requirement is covered by an appropriate test.