Add sign in flow using magic links

app/models/identity.rb

@@ -1,7 +1,11 @@
 class Identity < UntenantedRecord
   # This is used to instantiate an Identity-like object from the `identity_token` without hitting
   # the untenanted database. It is intended to be used with caching/etagging methods.
-  Mock = Struct.new(:id, :updated_at)
+  Mock = Struct.new(:id, :updated_at) do
+    def identity
+      Identity.find_signed(id)
+    end
+  end
 
   has_many :memberships, dependent: :destroy
 end