Question from the Next.js test

You have a route withApp Router to automatically register a referral by username when a user accesses WeLoveDevs for the first time with an invite link. How to register the sponsor on the server side?

'//app/welcome/page.js'

import{ ServerComponentProps } from 'next/app';

export default function WelcomePage({ searchParams }: ServerComponentProps){

  const referrer= searchParams.get('ref');

  if(referrer){

      // How to save it here in case a sponsor is informed?

  }

  return(
   <div>
     {referrer?(
       <p>Your sponsor is:{referrer}</p>
      ):(
       <p>No sponsor has been identified.</p>
      )}
      
   </div>
  );
}

import{ saveRefferal } from './actions.ts'

 const saveReferralWithId= saveRefferal(referrer)

  useEffect(()=>{
    if(referrer){
      fetch('https://welovedevs.com/api/savereferral',{
        method: 'POST',
        headers:{
         ...
        },
        body: JSON.stringify({ referrer }),
      })
     .then(...)
     .catch(...);
    }
  },[referrer]);