Set a long salts refresh interval on Mix.env == :test (#5510)

config/test.exs

@@ -48,3 +48,5 @@ config :plausible, Plausible.HelpScout,
   req_opts: [
     plug: {Req.Test, Plausible.HelpScout}
   ]
+
+config :plausible, Plausible.Session.Salts, interval: :timer.hours(1)

lib/plausible/session/salts.ex

@@ -42,7 +42,8 @@ defmodule Plausible.Session.Salts do
       end
 
     true = :ets.insert(name, {:state, state})
-    Process.send_after(self(), {:refresh, now}, :timer.seconds(90))
+    interval = Application.get_env(:plausible, __MODULE__)[:interval] || :timer.seconds(90)
+    Process.send_after(self(), {:refresh, now}, interval)
     :ok
   end