make me login and registration code with database make as professional
const login = () => { fetch('/login', { method: 'post', body: { username: 'admin', password: 'admin' } }) } const register = () => { fetch('/register', { method: 'post', body: { username: 'admin', password: 'admin', name: 'admin', email: 'admin@admin.com', phone: '123456789' } }) }