Update registration settings

app/controllers/admin/settings/registrations_controller.rb

@@ -3,7 +3,36 @@ class Admin::Settings::RegistrationsController < Admin::SettingsController
   def index
   end
 
-  def update
+  def create
+    @errors = ActiveModel::Errors.new(Setting.new)
+
+    setting_params.keys.each do |key|
+      next if setting_params[key].nil?
+
+      setting = Setting.new(var: key)
+      setting.value = setting_params[key].strip
+      unless setting.valid?
+        @errors.merge!(setting.errors)
+      end
+    end
+
+    if @errors.any?
+      render :index
+    end
+
+    setting_params.keys.each do |key|
+      Setting.send("#{key}=", setting_params[key].strip) unless setting_params[key].nil?
+    end
+
+    redirect_to admin_settings_registrations_path, flash: {
+      success: "Settings saved"
+    }
+  end
+
+  private
+
+  def setting_params
+    params.require(:setting).permit(:reserved_usernames)
   end
 
 end