Add structured app logs to admin/logs

app/controllers/admin/logs_controller.rb

@@ -10,7 +10,7 @@ class Admin::LogsController < Admin::ApplicationController
 
   def loggers
     @loggers ||= [
-      Gitlab::AppLogger,
+      Gitlab::AppJsonLogger,
       Gitlab::GitLogger,
       Gitlab::EnvironmentLogger,
       Gitlab::SidekiqLogger,

changelogs/unreleased/ag-addjson-log-to-admin-logs.yml

+---
+title: Replace unstructured application logs with structured (JSON) application logs in the admin interface
+merge_request: 24614
+author:
+type: other

spec/features/admin/admin_browses_logs_spec.rb

@@ -10,7 +10,7 @@ describe 'Admin browses logs' do
   it 'shows available log files' do
     visit admin_logs_path
 
-    expect(page).to have_link 'application.log'
+    expect(page).to have_link 'application_json.log'
     expect(page).to have_link 'git_json.log'
     expect(page).to have_link 'test.log'
     expect(page).to have_link 'sidekiq.log'