So, I was developing a Decentralized application with the main focus of making the transaction to a particular organization transparent, using tokens.
But the major problem I encountered was the inability of users to even buy the tokens in countries where such transactions are illegal as of now.

Basically, I just want to track a user_id with the transaction that they have made using our smart contract in solidity.

Is there a way to achieve this?

I was planning on using a way to have such information in each of the transactions made by such users (Not by their Addresses but through our smart contract.)

At one point I also thought of using a mapping between the user_id and the txn_hash, but it was not possible to incorporate txn hash as txn don't get confirmed before that.