First cut of a simplified "intro" UI layout (#265)

* First cut of a simplified "intro" UI layout

* Linter

* Add guest role and intro-only access

* Fix guest role UI defaults (#940)

Use enum predicate to avoid missing role helper.

* Remove legacy user role mapping (#941)

Drop the unused user role references in role normalization
and SSO role mapping forms to avoid implying a role that
never existed.

Refs: #0

* Remove role normalization (#942)

Remove role normalization

Roles are now stored directly without legacy mappings.

* Revert role mapping logic

* Remove `normalize_role_settings`

* Remove unnecessary migration

* Make `member` the default

* Broken `.erb`

---------

Signed-off-by: Juan José Mata <juanjo.mata@gmail.com>

app/views/registrations/new.html.erb

@@ -12,7 +12,7 @@
     <p class="text-secondary">
       <%= t(".invitation_message",
             inviter: @invitation.inviter.display_name,
-            role: t(".role_#{@invitation.role}")) %>
+            role: t(".role_#{@invitation.role}", default: @invitation.role.to_s.humanize.downcase)) %>
     </p>
   </div>
 <% end %>