class User {
    ...
    
    public function workspaces() {
        return $this->belongsToMany('App\Models\WorkspaceMember');
    }
}

class Workspace {
    ...
    
    public function members() {
        return $this->hasMany('App\Models\Workspacemember');
    }
}

class WorkspaceMember {
    ...

    getRoleAttribute() {
        ...
    }

    setRoleAttribute() {
        ...
    }
}