Improve session handling

Author: Unai Abrisketa

lib/beyond_api/session.rb

@@ -26,11 +26,17 @@ module BeyondApi
   autoload :WebhookSubscriptions,        "beyond_api/resources/webhook_subscriptions"
 
   class Session
+    class InvalidUriProtocolError < StandardError; end
+
     attr_reader :api_url
     attr_accessor :access_token, :refresh_token
 
     def initialize(api_url:, access_token: nil, refresh_token: nil)
-      @api_url = api_url
+      raise InvalidUriProtocolError, "Invalid URI protocol" unless api_url.start_with? "https://"
+
+      uri = URI.parse(api_url)
+
+      @api_url = "#{uri.scheme}://#{uri.host}/api"
       @access_token = access_token
       @refresh_token = refresh_token
     end