Automatic userId relation on creation

Is there a way to automatically provide a field

userId

userId

(from authenticable entity

User

User

) using the

Bearer

Bearer

token while item creation? I'd like to make the field

userId

userId

optional in the request, and provide the requesting user's

id

id

when not provided. I was thinking about using middlewares, but how do I access the current user?

Automatic userId relation on creation - Manifest