Add checking and updating DeepL usage information

lib/outlook/translators/deepl.ex

@@ -10,6 +10,12 @@ defmodule Outlook.Translators.Deepl do
     send(pid, {:progress, %{progress: nil}})
   end
 
+  def get_usage_counts(auth_key) do
+    response = HTTPoison.get!("https://api-free.deepl.com/v2/usage",
+      ["Authorization": "DeepL-Auth-Key #{auth_key}"])
+    Jason.decode!(response.body, keys: :atoms)
+  end
+
   # @options [ssl: [{:versions, [:'tlsv1.2']}], recv_timeout: 500]
 
   @doc """

lib/outlook/translators/deepl_account.ex

@@ -18,6 +18,6 @@ defmodule Outlook.Translators.DeeplAccount do
   def changeset(deepl_account, attrs) do
     deepl_account
     |> cast(attrs, [:name, :description, :auth_key, :character_limit, :character_count, :our_character_count, :user_id])
-    |> validate_required([:name, :description, :auth_key, :character_limit, :user_id])
+    |> validate_required([:name, :description, :auth_key, :user_id])
   end
 end