Hello I am a very experienced web dev who is brand new to Drupal and learning to build my first site in it.

I have a very simple site I am converting from pure code (html, css, jquery, angular, bootstrap, php) to drupal so that I can add a CMS backend to the site. On this site I need to track what ad campaign sent the user to the site to be stored with the users information later after they submit their email to be contacted again.

This is how it works currently on the non-drupal site: User clicks on a link on an 3rd party site that directs them to my-site.com/get-eBook.html?campaign=google. On get-eBook.html there is a menu item for /ebook-register.php, I use some PHP to grab the value of campaign from the URL and if it is not null I update the menu item to /ebook-register.php?campaign=google in order to pass the value along to the register page where it is used in a SQL statement and captured in the DB with the users email address.

Now I’m not sure how to accomplish the same thing in Drupal. I have my theme set up, I have two pages created (get-ebook and ebook-register) and I have my menu set up with the link to ebook-register. I however have no idea how I can grab the value of campaign on the get-ebook page and add that value onto the desired menu item being returned by the drupal core so that the value of campaign will be preserved when the user navigated from get-ebook to ebook-register.

Any ideas on how I can allow the menu to be maintained via the Drupal backend but still have the ability to dynamically add query parameters to the items after they’re returned from the core?