How to convert nested object to flat object?

[liaodalin19903]

How to convert nested object to flat object?

interface NestedUser {
  name: string;
  address: {
    street: string;
    city: string;
  };
}

interface FlatUser {
  'name': string;
  'address.street': string;
  'address.city': string;
}

please help with this.