fix bugs in the backend classes

src/services/system.ts

@@ -1,11 +1,17 @@
 import axios from 'axios';
 import { Configuration } from './configuration';
 import { Session } from './session';
+import { BackendReturnStatus, TimestampBackend } from '../types';
 
 export class System {
-  static async timestamp(): Promise<number> {
+  static async timestamp(): Promise<TimestampBackend> {
     const token = Session.bearerToken();
-    if (!token) return 0;
+    if (!token) {
+      return {
+        status: BackendReturnStatus.Unauthorized,
+        timestamp: 0,
+      };
+    }
 
     return axios
       .get<number>(`${Configuration.resourceServer}/system/timestamp`, {
@@ -13,7 +19,17 @@ export class System {
           Authorization: `Bearer ${token}`,
         },
       })
-      .then((response) => response.data)
-      .catch(() => 0);
+      .then((response) => {
+        return {
+          status: BackendReturnStatus.Ok,
+          timestamp: response.data,
+        };
+      })
+      .catch((err) => {
+        return {
+          status: err.response.status === 401 ? BackendReturnStatus.Unauthorized : BackendReturnStatus.Failure,
+          timestamp: 0,
+        };
+      });
   }
 }