Allow user to change default email

apps/fg_http/lib/fg_http/users.ex

@@ -40,6 +40,10 @@ defmodule FgHttp.Users do
     User.changeset(user, %{})
   end
 
+  def single_user? do
+    Repo.one(from u in User, select: count()) == 1
+  end
+
   # For now, assume first User is admin
   def admin do
     User |> first |> Repo.one()

apps/fg_http/lib/fg_http_web/templates/session/new.html.eex

@@ -13,7 +13,7 @@
       <div class="field">
         <%= label(:session, :email, class: "label") %>
         <div class="control">
-          <%= text_input(f, :email, email_field_opts()) %>
+          <%= text_input(f, :email, email_field_opts(class: "input")) %>
         </div>
         <p class="help is-danger">
           <%= error_tag f, :email %>

apps/fg_http/lib/fg_http_web/views/session_view.ex

@@ -2,12 +2,12 @@ defmodule FgHttpWeb.SessionView do
   use FgHttpWeb, :view
   alias FgHttp.Users
 
-  # Don't allow user to enter email if signups are disabled.
-  def email_field_opts do
-    if signups_disabled?() do
-      [class: "input", readonly: true, value: Users.admin_email()]
+  # Guess email if signups are disabled and only one user exists
+  def email_field_opts(opts \\ []) when is_list(opts) do
+    if Users.single_user?() and signups_disabled?() do
+      opts ++ [value: Users.admin_email()]
     else
-      [class: "input"]
+      opts
     end
   end