Feature Request: Let admins authenticate users without password

[vypxl]

I am playing around with passkey based login, and got it to work, the only problem is, when I successfully authenticated
the user with their passkey, I have no way to let pocketbase know that.

Until #406 is implemented, I want to propose a way for the backend to authenticate a user without their intervention.

Something along the lines of pb.collection('users').authManual(userID). This could be set to only be accessible by admins, so the backend could authenticate as an admin and log in a user after they successfully presented a passkey.

[ganigeorgiev]

Option for admins to generate auth user tokens by user id eventually will be handled in #718.

As a workaround for now, you can register a custom Go route and use the tokens.NewRecordAuthToken() to return a record token by the record id (see also Fetch single record).