```ruby
require "active_rest_client"
require "click_meter/configuration"

module ClickMeter
  class Base < ActiveRestClient::Base
    include Configuration

  	before_request :add_authentication_details

  	private

  	def add_authentication_details(name, request)
  		request.headers["X-Clickmeter-Authkey"] = self.class.auth_key
  	end
  end
end
```

Set request type for the request to JSON; fix NoMethodError if auth_key is nil
user
```ruby
require "active_rest_client"
require "click_meter/configuration"

module ClickMeter
  class Base < ActiveRestClient::Base
    include Configuration

  	before_request :add_authentication_details
    request_body_type :json

  	private

  	def add_authentication_details(name, request)
  		request.headers["X-Clickmeter-Authkey"] = self.class.auth_key.to_s
  	end
  end
end
```
assistant