GRN2-6: Added the ability for admins to specify registration method (#520)

* Added the ability to invite users

* Small bug fix

* Added the ability to approve/decline users

* Small bug fixes

* More bug fixes

* More minor changes

* Final changes

app/models/setting.rb

@@ -37,6 +37,8 @@ class Setting < ApplicationRecord
         Rails.configuration.branding_image_default
       when "Primary Color"
         Rails.configuration.primary_color_default
+      when "Registration Method"
+        Rails.configuration.registration_method_default
       end
     end
   end