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/views/about/index.html.haml

@@ -8,7 +8,7 @@
   %meta{ property: 'og:site_name', content: 'Mastodon' }/
   %meta{ property: 'og:type', content: 'website' }/
   %meta{ property: 'og:title', content: Rails.configuration.x.local_domain }/
-  %meta{ property: 'og:description', content: "Mastodon is a free, open-source social network server. A decentralized alternative to commercial platforms, it avoids the risks of a single company monopolizing your communication. Anyone can run Mastodon and participate in the social network seamlessly" }/
+  %meta{ property: 'og:description', content: @description.blank? ? "Mastodon is a free, open-source social network server. A decentralized alternative to commercial platforms, it avoids the risks of a single company monopolizing your communication. Anyone can run Mastodon and participate in the social network seamlessly" : strip_tags(@description) }/
   %meta{ property: 'og:image', content: asset_url('mastodon_small.jpg') }/
   %meta{ property: 'og:image:width', content: '400' }/
   %meta{ property: 'og:image:height', content: '400' }/
@@ -24,6 +24,9 @@
 
   .screenshot= image_tag 'screenshot.png'
 
+  - unless @description.blank?
+    %p= @description.html_safe
+
   .actions
     .info
       = link_to t('about.terms'), terms_path

app/views/admin/settings/index.html.haml

@@ -0,0 +1,22 @@
+- content_for :page_title do
+  Site Settings
+
+%table.table
+  %colgroup
+    %col{ width: '35%' }/
+  %thead
+    %tr
+      %th Setting
+      %th Click to edit
+  %tbody
+    %tr
+      %td
+        %strong Site description
+        %br/
+        Displayed as a paragraph on the frontpage and used as a meta tag.
+        %br/
+        You can use HTML tags, in particular
+        %code= '<a>'
+        and
+        %code= '<em>'
+      %td= best_in_place @settings['site_description'], :value, as: :textarea, url: admin_setting_path(@settings['site_description'])

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

@@ -6,14 +6,14 @@
 
   = f.input :locale, collection: I18n.available_locales, wrapper: :with_label, include_blank: false, label_method: lambda { |locale| human_locale(locale) }
 
-  = f.simple_fields_for :notification_emails, current_user.settings(:notification_emails) do |ff|
+  = f.simple_fields_for :notification_emails, hash_to_object(current_user.settings.notification_emails) do |ff|
     = ff.input :follow, as: :boolean, wrapper: :with_label
     = ff.input :follow_request, as: :boolean, wrapper: :with_label
     = ff.input :reblog, as: :boolean, wrapper: :with_label
     = ff.input :favourite, as: :boolean, wrapper: :with_label
     = ff.input :mention, as: :boolean, wrapper: :with_label
 
-  = f.simple_fields_for :interactions, current_user.settings(:interactions) do |ff|
+  = f.simple_fields_for :interactions, hash_to_object(current_user.settings.interactions) do |ff|
     = ff.input :must_be_follower, as: :boolean, wrapper: :with_label
     = ff.input :must_be_following, as: :boolean, wrapper: :with_label