fix: Update unread_messages count in WhatsApp inboxes (#6154)

* fix: Update unread_count from backend instead of computing on the frontend

* Fix spec

* Remove status indicator on private notifications

* CodeClimate fix

* CodeClimate

app/javascript/dashboard/store/modules/specs/conversations/mutations.spec.js

@@ -103,6 +103,7 @@ describe('#mutations', () => {
               created_at: 1602256198,
             },
           ],
+          unread_count: 0,
           timestamp: 1602256198,
         },
       ]);
@@ -130,6 +131,7 @@ describe('#mutations', () => {
               created_at: 1602256198,
             },
           ],
+          unread_count: 0,
           timestamp: 1602256198,
         },
       ]);