Pull request: replace empty string with load_balance for upstream_mode

Squashed commit of the following:

commit 69d2310
Merge: 76df040 58b47ad
Author: Ildar Kamalov <ik@adguard.com>
Date:   Tue Jan 16 12:22:52 2024 +0300

    Merge branch 'master' into ADG-7965

commit 76df040
Author: Ildar Kamalov <ik@adguard.com>
Date:   Fri Jan 12 13:18:21 2024 +0300

    remove changelog

commit e79b7bf
Merge: df0f189 1e0ff4d
Author: Ildar Kamalov <ik@adguard.com>
Date:   Fri Jan 12 13:17:50 2024 +0300

    Merge branch 'master' into ADG-7965

commit df0f189
Author: Ildar Kamalov <ik@adguard.com>
Date:   Wed Jan 10 19:21:34 2024 +0300

    fix changelog

commit 8143087
Author: Ildar Kamalov <ik@adguard.com>
Date:   Wed Jan 10 18:04:24 2024 +0300

    handle empty string

commit e9e672c
Author: Ildar Kamalov <ik@adguard.com>
Date:   Tue Jan 9 16:15:02 2024 +0300

    changelog

commit 34fb9b7
Author: Ildar Kamalov <ik@adguard.com>
Date:   Tue Jan 9 13:23:09 2024 +0300

    ADG-7965 replace empty string with load_balance for upstream_mode

client/src/helpers/constants.js

@@ -436,7 +436,7 @@ export const SCHEME_TO_PROTOCOL_MAP = {
 export const DNS_REQUEST_OPTIONS = {
     PARALLEL: 'parallel',
     FASTEST_ADDR: 'fastest_addr',
-    LOAD_BALANCING: '',
+    LOAD_BALANCING: 'load_balance',
 };
 
 export const DHCP_FORM_NAMES = {

client/src/reducers/dnsConfig.js

@@ -1,7 +1,7 @@
 import { handleActions } from 'redux-actions';
 
 import * as actions from '../actions/dnsConfig';
-import { ALL_INTERFACES_IP, BLOCKING_MODES } from '../helpers/constants';
+import { ALL_INTERFACES_IP, BLOCKING_MODES, DNS_REQUEST_OPTIONS } from '../helpers/constants';
 
 const DEFAULT_BLOCKING_IPV4 = ALL_INTERFACES_IP;
 const DEFAULT_BLOCKING_IPV6 = '::';
@@ -15,6 +15,7 @@ const dnsConfig = handleActions(
                 blocking_ipv4,
                 blocking_ipv6,
                 upstream_dns,
+                upstream_mode,
                 fallback_dns,
                 bootstrap_dns,
                 local_ptr_upstreams,
@@ -33,6 +34,7 @@ const dnsConfig = handleActions(
                 local_ptr_upstreams: (local_ptr_upstreams && local_ptr_upstreams.join('\n')) || '',
                 ratelimit_whitelist: (ratelimit_whitelist && ratelimit_whitelist.join('\n')) || '',
                 processingGetConfig: false,
+                upstream_mode: upstream_mode === '' ? DNS_REQUEST_OPTIONS.LOAD_BALANCING : upstream_mode,
             };
         },