Add server banner to web app, add GET /api/v2/instance to REST API (#19294)

Cherry-picked d2528b26b6

Conflicts:
- `app/serializers/initial_state_serializer.rb`:
  Upstream changed stuff, we had extra attributes.
  Applied upstream changes while keeping our extra attributes.
- `app/serializers/rest/instance_serializer.rb`:
  Upstream actually moved that to `app/serializers/rest/v1/instance_serializer.rb`,
  so updated that file by keeping our extra attributes, and took upstream's
  version of `app/serializers/rest/instance_serializer.rb`.
- `spec/views/about/show.html.haml_spec.rb`:
  Took upstream's version.

app/views/about/more.html.haml

@@ -8,7 +8,7 @@
   .column-0
     .public-account-header.public-account-header--no-bar
       .public-account-header__image
-        = image_tag @instance_presenter.hero&.file&.url || @instance_presenter.thumbnail&.file&.url || asset_pack_path('media/images/preview.png'), alt: @instance_presenter.site_title, class: 'parallax'
+        = image_tag @instance_presenter.hero&.file&.url || @instance_presenter.thumbnail&.file&.url || asset_pack_path('media/images/preview.png'), alt: @instance_presenter.title, class: 'parallax'
 
   .column-1
     .landing-page__call-to-action{ dir: 'ltr' }
@@ -30,14 +30,14 @@
     .contact-widget
       %h4= t 'about.administered_by'
 
-      = account_link_to(@instance_presenter.contact_account)
+      = account_link_to(@instance_presenter.contact.account)
 
-      - if @instance_presenter.site_contact_email.present?
+      - if @instance_presenter.contact.email.present?
         %h4
           = succeed ':' do
             = t 'about.contact'
 
-        = mail_to @instance_presenter.site_contact_email, nil, title: @instance_presenter.site_contact_email
+        = mail_to @instance_presenter.contact.email, nil, title: @instance_presenter.contact.email
 
   .column-3
     = render 'application/flashes'

app/views/about/show.html.haml

@@ -53,11 +53,11 @@
 
       .hero-widget
         .hero-widget__img
-          = image_tag @instance_presenter.hero&.file&.url || @instance_presenter.thumbnail&.file&.url || asset_pack_path('media/images/preview.png'), alt: @instance_presenter.site_title
+          = image_tag @instance_presenter.hero&.file&.url || @instance_presenter.thumbnail&.file&.url || asset_pack_path('media/images/preview.png'), alt: @instance_presenter.title
 
         .hero-widget__text
           %p
-            = @instance_presenter.site_short_description.html_safe.presence || t('about.about_mastodon_html')
+            = @instance_presenter.description.html_safe.presence || t('about.about_mastodon_html')
             = link_to about_more_path do
               = t('about.learn_more')
               = fa_icon 'angle-double-right'
@@ -66,7 +66,7 @@
           .hero-widget__footer__column
             %h4= t 'about.administered_by'
 
-            = account_link_to @instance_presenter.contact_account
+            = account_link_to @instance_presenter.contact.account
 
           .hero-widget__footer__column
             %h4= t 'about.server_stats'

app/views/application/_sidebar.html.haml

@@ -1,9 +1,9 @@
 .hero-widget
   .hero-widget__img
-    = image_tag @instance_presenter.hero&.file&.url || @instance_presenter.thumbnail&.file&.url || asset_pack_path('media/images/preview.png'), alt: @instance_presenter.site_title
+    = image_tag @instance_presenter.hero&.file&.url || @instance_presenter.thumbnail&.file&.url || asset_pack_path('media/images/preview.png'), alt: @instance_presenter.title
 
   .hero-widget__text
-    %p= @instance_presenter.site_short_description.html_safe.presence || t('about.about_mastodon_html')
+    %p= @instance_presenter.description.html_safe.presence || t('about.about_mastodon_html')
 
 - if Setting.trends && !(user_signed_in? && !current_user.setting_trends)
   - trends = Trends.tags.query.allowed.limit(3)

app/views/privacy/show.html.haml

@@ -4,6 +4,6 @@
 .grid
   .column-0
     .box-widget
-      .rich-formatting= @instance_presenter.site_terms.html_safe.presence || t('terms.body_html')
+      .rich-formatting= @instance_presenter.privacy_policy.html_safe.presence || t('terms.body_html')
   .column-1
     = render 'application/sidebar'

app/views/shared/_og.html.haml

@@ -1,12 +1,12 @@
 - thumbnail     = @instance_presenter.thumbnail
-- description ||= strip_tags(@instance_presenter.site_short_description.presence || t('about.about_mastodon_html'))
+- description ||= strip_tags(@instance_presenter.description.presence || t('about.about_mastodon_html'))
 
 %meta{ name: 'description', content: description }/
 
 = opengraph 'og:site_name', t('about.hosted_on', domain: site_hostname)
 = opengraph 'og:url', url_for(only_path: false)
 = opengraph 'og:type', 'website'
-= opengraph 'og:title', @instance_presenter.site_title
+= opengraph 'og:title', @instance_presenter.title
 = opengraph 'og:description', description
 = opengraph 'og:image', full_asset_url(thumbnail&.file&.url || asset_pack_path('media/images/preview.png', protocol: :request))
 = opengraph 'og:image:width', thumbnail ? thumbnail.meta['width'] : '1200'