Add login view model

app/src/main/java/com/navi/medici/android_customer_app/login/LoginViewModel.kt

@@ -1,16 +1,13 @@
-package com.navi.medici.android_customer_app.view_models
+package com.navi.medici.android_customer_app.login
 
 import androidx.lifecycle.ViewModel
 
 class LoginViewModel : ViewModel() {
-    private var phoneNumber = String()
+    private val login = Login("")
 
     fun onChangePhoneNumber(phoneNumber: String) {
-        this.phoneNumber = phoneNumber
-        if (isValidPhoneNumber()) {
-
+        login.phoneNumber = phoneNumber
+        if (login.isValidPhoneNumber()) {
         }
     }
-
-    private fun isValidPhoneNumber(): Boolean = phoneNumber.length == 10
 }