move new teacher form to marketing site

fixes CNVS-22581

test plan
 - setup open registration
 - in console set root_account setting
 - a = Account.root_accounts.active.find(id)
 - a.settings[:fft_registration_url] = "http://www.canvaslms.com/try-canvas?lead_source_description=canvas.instructure.com_fft_canvas_"
 - a.save!
 - click on "I'm a teacher" YOUR_CANVAS/register_from_website
 - it should redirect to canvaslms try canvas link
 - remove setting
 - it should bring up form to register locally

Change-Id: I14f6daacffceda4dd25b4829558f9f9472618104
Reviewed-on: https://gerrit.instructure.com/61446
Reviewed-by: Jacob Fugal <jacob@instructure.com>
QA-Review: August Thornton <august@instructure.com>
Product-Review: Rob Orton <rob@instructure.com>
Tested-by: Jenkins

Author: roor0

app/models/account.rb

@@ -176,6 +176,7 @@ def default_locale(recurse = false)
   add_setting :login_handle_name, root_only: true
   add_setting :change_password_url, root_only: true
   add_setting :unknown_user_url, root_only: true
+  add_setting :fft_registration_url, root_only: true
 
   add_setting :restrict_student_future_view, :boolean => true, :default => false, :inheritable => true
   add_setting :restrict_student_past_view, :boolean => true, :default => false, :inheritable => true

app/views/users/new.html.erb

@@ -17,7 +17,11 @@
     <h2 id="registration_video"><a href="http://vimeo.com/35336470" title="Play the Canvas introduction video">Watch a Video</a></h2>
     <div id="registration_options">
       <h2>Sign up now, it's free!</h2>
-      <a href="#" id="signup_teacher" class="signup_link" data-template="teacherDialog" title="Teacher Signup">I'm a Teacher</a>
+      <% if (url = @domain_root_account.settings[:fft_registration_url]) %>
+        <a id="signup_teacher" href=<%= url %> title="Teacher Signup">I'm a Teacher</a>
+      <% else %>
+        <a href="#" id="signup_teacher" class="signup_link" data-template="teacherDialog" title="Teacher Signup">I'm a Teacher</a>
+      <% end %>
       <a href="#" id="signup_student" class="signup_link" data-template="studentDialog" title="Student Signup">I'm a Student</a>
       <%= link_to_parent_signup(@domain_root_account.parent_auth_type) %>
     </div>