feat: Line Channel (#2904)

- Ability to configure line bots as a channel in chatwoot
- Receive a message sent to the line bot in chatwoot
- Ability to reply to line users from chatwoot

fixes: #2738

app/javascript/shared/mixins/configMixin.js

@@ -3,9 +3,6 @@ export default {
     hostURL() {
       return window.chatwootConfig.hostURL;
     },
-    twilioCallbackURL() {
-      return `${this.hostURL}/twilio/callback`;
-    },
     vapidPublicKey() {
       return window.chatwootConfig.vapidPublicKey;
     },