Question: about the design of ClientInfo interface

[yangtuooc]

I have a question about the design of the ClientInfo interface, specifically about the GetUserID() method:

type ClientInfo interface {
GetID() string
GetSecret() string
GetDomain() string
IsPublic() bool
GetUserID() string // <-- This method
}

According to OAuth2 specification, a Client typically represents a third-party application. However, the GetUserID() method in the interface seems to suggest a one-to-one relationship between a Client and a User.

Questions:

1. What's the intended use case for GetUserID()?
2. How should this be used in scenarios where one Client serves multiple users?

I'm trying to understand the design rationale to better implement this interface in my application.