Redesign forms, verify link ownership with rel="me" (#8703)

* Verify link ownership with rel="me"

* Add explanation about verification to UI

* Perform link verifications

* Add click-to-copy widget for verification HTML

* Redesign edit profile page

* Redesign forms

* Improve responsive design of settings pages

* Restore landing page sign-up form

* Fix typo

* Support <link> tags, add spec

* Fix links not being verified on first discovery and passive updates

app/views/auth/confirmations/new.html.haml

@@ -4,7 +4,8 @@
 = simple_form_for(resource, as: resource_name, url: confirmation_path(resource_name), html: { method: :post }) do |f|
   = render 'shared/error_messages', object: resource
 
-  = f.input :email, autofocus: true, required: true, placeholder: t('simple_form.labels.defaults.email'), input_html: { 'aria-label' => t('simple_form.labels.defaults.email') }
+  .fields-group
+    = f.input :email, autofocus: true, wrapper: :with_label, label: t('simple_form.labels.defaults.email'), input_html: { 'aria-label' => t('simple_form.labels.defaults.email') }, hint: false
 
   .actions
     = f.button :button, t('auth.resend_confirmation'), type: :submit