canvas-lms/app/messages/new_user.summary.erb

<% define_content :link do %>
  <%= user_url(asset) %>
<% end %>
<% define_content :subject do %>
  <%= t :subject, "New User" %>
<% end %>

<%= t :body, "A new user, %{user}, has just registered for the account %{account}", :user => asset.name, :account => asset.account.name %>