Add partial template for in_forward setting

This change will improve usability after some more changes.

Signed-off-by: Kenji Okimoto <okimoto@clear-code.com>

app/views/fluentd/settings/in_forward/_form.html.haml

@@ -0,0 +1,15 @@
+= render "shared/setting_errors"
+
+- # NOTE: plugin_setting_form_action_url is defined at SettingConcern
+= form_for(@setting, url: plugin_setting_form_action_url(@fluentd), html: {class: "ignore-rails-error-div"}) do |f|
+  - @setting.common_options.each do |key|
+    = field(f, key)
+
+  .well.well-sm
+    %h4{"data-toggle" => "collapse", "href" => "#advanced-setting"}
+      = icon('fa-caret-down')
+      = t('terms.advanced_setting')
+    #advanced-setting.collapse
+      TODO
+
+  = f.submit t('fluentd.common.finish'), class: "btn btn-lg btn-primary pull-right"

app/views/shared/settings/show.html.haml

@@ -5,4 +5,7 @@
   .card-body.bg-light
     = raw t("fluentd.settings.#{target_plugin_name}.option_guide")
 
-= render "shared/settings/form"
+- if lookup_context.exists?("form", controller.controller_path, true)
+  = render "#{controller.controller_path}/form"
+- else
+  = render "shared/settings/form"