Ensure more of Sidekiq logs are in JSON

Because the Sidekiq log formatter was initialized after Sidekiq
initialized Redis, we would see some unstructured logs emitted at boot.
To fix this, move the log formatter up earlier in the Sidekiq init
process.

Closes https://gitlab.com/gitlab-org/gitlab/issues/208922

config/initializers/sidekiq.rb

@@ -36,15 +36,6 @@ use_sidekiq_legacy_memory_killer = !use_sidekiq_daemon_memory_killer
 use_request_store = ENV.fetch('SIDEKIQ_REQUEST_STORE', 1).to_i.nonzero?
 
 Sidekiq.configure_server do |config|
-  config.redis = queues_config_hash
-
-  config.server_middleware(&Gitlab::SidekiqMiddleware.server_configurator({
-    metrics: Settings.monitoring.sidekiq_exporter,
-    arguments_logger: ENV['SIDEKIQ_LOG_ARGUMENTS'] && !enable_json_logs,
-    memory_killer: enable_sidekiq_memory_killer && use_sidekiq_legacy_memory_killer,
-    request_store: use_request_store
-  }))
-
   if enable_json_logs
     Sidekiq.logger.formatter = Gitlab::SidekiqLogging::JSONFormatter.new
     config.options[:job_logger] = Gitlab::SidekiqLogging::StructuredLogger
@@ -54,6 +45,15 @@ Sidekiq.configure_server do |config|
     config.error_handlers << Gitlab::SidekiqLogging::ExceptionHandler.new
   end
 
+  config.redis = queues_config_hash
+
+  config.server_middleware(&Gitlab::SidekiqMiddleware.server_configurator({
+    metrics: Settings.monitoring.sidekiq_exporter,
+    arguments_logger: ENV['SIDEKIQ_LOG_ARGUMENTS'] && !enable_json_logs,
+    memory_killer: enable_sidekiq_memory_killer && use_sidekiq_legacy_memory_killer,
+    request_store: use_request_store
+  }))
+
   config.client_middleware(&Gitlab::SidekiqMiddleware.client_configurator)
 
   config.on :startup do