Moved the upgrade alert out of the `hasSections` condition

What does this MR do and why?

The MR introduces a minor refactoring for the "GitLab for Slack app" alert, introduced in !102661 (merged). Previously, the alert has been placed within the hasSections condition. However, it might happen that the integration doesn't have sections even thought the fields are passed down the component.

This MR fixes this scenario by moving the markup outside of hasSections condition to show it even if there are only fields without a section.

Screenshots or screen recordings

	Before	After
With sections
Without sections

How to set up and validate locally

1. Enable the feature flag in the rails console (rails c): Feature.enable(:integration_slack_app_notifications)
2. The simplest to get sections and fields without the sections is to apply one of the patches below:

Patch for fields only

diff --git a/ee/app/models/integrations/gitlab_slack_application.rb b/ee/app/models/integrations/gitlab_slack_application.rb
index 80b83db36cdb..ad7cf2497ca8 100644
--- a/ee/app/models/integrations/gitlab_slack_application.rb
+++ b/ee/app/models/integrations/gitlab_slack_application.rb
@@ -41,7 +41,38 @@ def editable?
 
     override :fields
     def fields
-      return [] unless editable?
+      # return [] unless editable?
+      [
+        {
+          type: 'checkbox',
+          name: 'notify_only_broken_pipelines',
+          section: SECTION_TYPE_CONNECTION,
+          help: 'Do not send notifications for successful pipelines.'
+        }.freeze,
+        {
+          type: 'select',
+          name: 'branches_to_be_notified',
+          section: SECTION_TYPE_CONNECTION,
+          title: s_('Integrations|Branches for which notifications are to be sent'),
+          choices: Integrations::Slack.branch_choices
+        }.freeze,
+        {
+          type: 'text',
+          name: 'labels_to_be_notified',
+          section: SECTION_TYPE_CONNECTION,
+          placeholder: '~backend,~frontend',
+          help: 'Send notifications for issue, merge request, and comment events with the listed labels only. Leave blank to receive notifications for all events.'
+        }.freeze,
+        {
+          type: 'select',
+          section: SECTION_TYPE_CONNECTION,
+          name: 'labels_to_be_notified_behavior',
+          choices: [
+            ['Match any of the labels', MATCH_ANY_LABEL],
+            ['Match all of the labels', MATCH_ALL_LABELS]
+          ]
+        }.freeze
+      ].freeze
 
       super
     end

Patch for fields with sections

diff --git a/ee/app/models/integrations/gitlab_slack_application.rb b/ee/app/models/integrations/gitlab_slack_application.rb
index 80b83db36cdb..21eaccdf7b0a 100644
--- a/ee/app/models/integrations/gitlab_slack_application.rb
+++ b/ee/app/models/integrations/gitlab_slack_application.rb
@@ -41,11 +41,53 @@ def editable?
 
     override :fields
     def fields
-      return [] unless editable?
+      # return [] unless editable?
+      [
+        {
+          type: 'checkbox',
+          name: 'notify_only_broken_pipelines',
+          section: SECTION_TYPE_CONNECTION,
+          help: 'Do not send notifications for successful pipelines.'
+        }.freeze,
+        {
+          type: 'select',
+          name: 'branches_to_be_notified',
+          section: SECTION_TYPE_CONNECTION,
+          title: s_('Integrations|Branches for which notifications are to be sent'),
+          choices: Integrations::Slack.branch_choices
+        }.freeze,
+        {
+          type: 'text',
+          name: 'labels_to_be_notified',
+          section: SECTION_TYPE_CONNECTION,
+          placeholder: '~backend,~frontend',
+          help: 'Send notifications for issue, merge request, and comment events with the listed labels only. Leave blank to receive notifications for all events.'
+        }.freeze,
+        {
+          type: 'select',
+          section: SECTION_TYPE_CONNECTION,
+          name: 'labels_to_be_notified_behavior',
+          choices: [
+            ['Match any of the labels', MATCH_ANY_LABEL],
+            ['Match all of the labels', MATCH_ALL_LABELS]
+          ]
+        }.freeze
+      ].freeze
 
       super
     end
 
+    def sections
+      [
+        {
+          type: SECTION_TYPE_CONNECTION,
+          title: s_('Integrations|Notifications'),
+          description: help
+        }
+      ]
+    end
+
+
     override :configurable_events
     def configurable_events
       return [] unless editable?

MR acceptance checklist

This checklist encourages us to confirm any changes have been analyzed to reduce risks in quality, performance, reliability, security, and maintainability.

• I have evaluated the MR acceptance checklist for this MR.

Related to #378218 (closed)