PLT-3193 Add channel notification preferences for push and email noti… (#5500)

* PLT-3193 Add channel notification preferences for push and email notifications

* unit tests, model validation and localization

* Feedback review

* Adding back allowFromCache check

* Setting push and email to use default settings

* Move props as constants

* address feedback

i18n/en.json

@@ -3519,10 +3519,18 @@
     "id": "model.channel_member.is_valid.role.app_error",
     "translation": "Invalid role"
   },
+  {
+    "id": "model.channel_member.is_valid.email_value.app_error",
+    "translation": "Invalid email notification value"
+  },
   {
     "id": "model.channel_member.is_valid.unread_level.app_error",
     "translation": "Invalid mark unread level"
   },
+  {
+    "id": "model.channel_member.is_valid.push_level.app_error",
+    "translation": "Invalid push notification level"
+  },
   {
     "id": "model.channel_member.is_valid.user_id.app_error",
     "translation": "Invalid user id"