Add custom closed registrations message to landing page when set (#10347)

app/javascript/styles/mastodon/forms.scss

@@ -475,6 +475,42 @@ code {
       }
     }
   }
+
+  &__overlay-area {
+    position: relative;
+
+    &__overlay {
+      position: absolute;
+      top: 0;
+      left: 0;
+      width: 100%;
+      height: 100%;
+      display: flex;
+      justify-content: center;
+      align-items: center;
+      background: rgba($ui-base-color, 0.65);
+      backdrop-filter: blur(2px);
+      border-radius: 4px;
+
+      &__content {
+        text-align: center;
+
+        &.rich-formatting {
+          &,
+          p {
+            color: $primary-text-color;
+          }
+        }
+      }
+    }
+  }
+}
+
+.block-icon {
+  display: block;
+  margin: 0 auto;
+  margin-bottom: 10px;
+  font-size: 24px;
 }
 
 .flash-message {

app/presenters/instance_presenter.rb

@@ -8,6 +8,7 @@ class InstancePresenter
     :site_description,
     :site_extended_description,
     :site_terms,
+    :closed_registrations_message,
     to: Setting
   )
 

app/views/about/_registration.html.haml

 = simple_form_for(new_user, url: user_registration_path) do |f|
-  %p.lead= t('about.federation_hint_html', instance: content_tag(:strong, site_hostname))
+  .simple_form__overlay-area
+    %p.lead= t('about.federation_hint_html', instance: content_tag(:strong, site_hostname))
 
-  .fields-group
-    = f.simple_fields_for :account do |account_fields|
-      = account_fields.input :username, wrapper: :with_label, autofocus: true, label: false, required: true, input_html: { 'aria-label' => t('simple_form.labels.defaults.username'), :autocomplete => 'off', placeholder: t('simple_form.labels.defaults.username') }, append: "@#{site_hostname}", hint: false, disabled: closed_registrations?
+    .fields-group
+      = f.simple_fields_for :account do |account_fields|
+        = account_fields.input :username, wrapper: :with_label, autofocus: true, label: false, required: true, input_html: { 'aria-label' => t('simple_form.labels.defaults.username'), :autocomplete => 'off', placeholder: t('simple_form.labels.defaults.username') }, append: "@#{site_hostname}", hint: false, disabled: closed_registrations?
 
-    = f.input :email, placeholder: t('simple_form.labels.defaults.email'), required: true, input_html: { 'aria-label' => t('simple_form.labels.defaults.email'), :autocomplete => 'off' }, hint: false, disabled: closed_registrations?
-    = f.input :password, placeholder: t('simple_form.labels.defaults.password'), required: true, input_html: { 'aria-label' => t('simple_form.labels.defaults.password'), :autocomplete => 'off' }, hint: false, disabled: closed_registrations?
-    = f.input :password_confirmation, placeholder: t('simple_form.labels.defaults.confirm_password'), required: true, input_html: { 'aria-label' => t('simple_form.labels.defaults.confirm_password'), :autocomplete => 'off' }, hint: false, disabled: closed_registrations?
+      = f.input :email, placeholder: t('simple_form.labels.defaults.email'), required: true, input_html: { 'aria-label' => t('simple_form.labels.defaults.email'), :autocomplete => 'off' }, hint: false, disabled: closed_registrations?
+      = f.input :password, placeholder: t('simple_form.labels.defaults.password'), required: true, input_html: { 'aria-label' => t('simple_form.labels.defaults.password'), :autocomplete => 'off' }, hint: false, disabled: closed_registrations?
+      = f.input :password_confirmation, placeholder: t('simple_form.labels.defaults.confirm_password'), required: true, input_html: { 'aria-label' => t('simple_form.labels.defaults.confirm_password'), :autocomplete => 'off' }, hint: false, disabled: closed_registrations?
 
-  .fields-group
-    = f.input :agreement, as: :boolean, wrapper: :with_label, label: t('auth.checkbox_agreement_html', rules_path: about_more_path, terms_path: terms_path), disabled: closed_registrations?
+    .fields-group
+      = f.input :agreement, as: :boolean, wrapper: :with_label, label: t('auth.checkbox_agreement_html', rules_path: about_more_path, terms_path: terms_path), disabled: closed_registrations?
 
-  .actions
-    = f.button :button, sign_up_message, type: :submit, class: 'button button-primary', disabled: closed_registrations?
+    .actions
+      = f.button :button, sign_up_message, type: :submit, class: 'button button-primary', disabled: closed_registrations?
+
+    - if closed_registrations? && @instance_presenter.closed_registrations_message.present?
+      .simple_form__overlay-area__overlay
+        .simple_form__overlay-area__overlay__content.rich-formatting
+          .block-icon= fa_icon 'warning'
+          = @instance_presenter.closed_registrations_message.html_safe