How to add a parameter to request before validation?

Question

Laravel

Goodnight. I came across this case:

$request->fingerprint = $gpg->getFingerprint($request->public_key);

        $this->validate($data, [
            'login' => 'required|unique:users|max:10',
            'name' => 'required|max:10',
            'public_key' => 'required',
            'fingerprint' => 'required|unique:users'
        ]);

I work with GnuPG and need to check the fingerprint in the database, but to get it, you first need to extract it from the function, ajax is not considered, since there is a complete no js solution, that is, it will not be possible to get it before the request is formed. And with this addition, the validator swears that the fingerprint is an empty field. That is the error 'Fingerprint is required'. I tried to remove required, it sends null to the database, but when outputting via dd request'a, this parameter is available.
How can you act in such a situation?
Thanks in advance.

Answer 1

$request->merge()
But in general, I recommend discovering such a thing as a form request.