flame/policy.go
func DefaultGrantStrategy(scope oauth2.Scope, _ Client, _ ResourceOwner) (oauth2.Scope, error) {
	// check scope
	if !scope.Empty() {
		return nil, ErrInvalidScope
	}

	return scope, nil
}
func DefaultGrantStrategy(scope oauth2.Scope, _ Client, _ ResourceOwner) (oauth2.Scope, error) {
	// check scope
	if !scope.Empty() {
		return nil, ErrInvalidScope
	}

	return scope, nil
}
// DefaultGrantStrategy grants only empty scopes.