Implement checkin job for backups.

app/src/main/java/org/thoughtcrime/securesms/backup/v2/BackupRepository.kt

@@ -132,6 +132,19 @@ object BackupRepository {
     }
   }
 
+  /**
+   * Refreshes backup via server
+   */
+  fun refreshBackup(): NetworkResult<Unit> {
+    return initBackupAndFetchAuth()
+      .then { accessPair ->
+        AppDependencies.archiveApi.refreshBackup(
+          aci = SignalStore.account.requireAci(),
+          archiveServiceAccess = accessPair.messageBackupAccess
+        )
+      }
+  }
+
   /**
    * Gets the free storage space in the device's data partition.
    */