Application Authentication with callback url

Hi There , I want to know about any provision of sending the authentication token to the callback generation rest api call so that once the callback happens , we may get that token back with the request. I know we can get callback key alongwith the request but my usecase is as below, Once i send the document with package from my application which runs its own authentication session , i will set in-person signing true.Then i will generate token with any signer and get the access session which opens up the signing url for in-person signing . Now once i sign the document for which i have set the callback notification , i get the request payload but i also want to get my session token alongwith it which will different for different users of my application .i.e while doing this process from any app login , i want to send my login token and get it back with the callback url so that i can mark changes in my application for which i need to get the token back for the user who carried this process. I hope you understand my point , pleas help me on this,