Migrate from ledermann/rails-settings to rails-settings-cached which allows global settings

with YAML-defined defaults. Add admin page for editing global settings. Add "site_description"
setting that would show as a paragraph on the frontpage

app/controllers/admin/settings_controller.rb

@@ -0,0 +1,25 @@
+# frozen_string_literal: true
+
+class Admin::SettingsController < ApplicationController
+  before_action :require_admin!
+
+  layout 'admin'
+
+  def index
+    @settings = Setting.all_as_records
+  end
+
+  def update
+    @setting = Setting.where(var: params[:id]).first_or_initialize(var: params[:id])
+
+    if @setting.value != params[:setting][:value]
+      @setting.value = params[:setting][:value]
+      @setting.save
+    end
+
+    respond_to do |format|
+      format.html { redirect_to admin_settings_path }
+      format.json { respond_with_bip(@setting) }
+    end
+  end
+end