Allow user to register with custom language

lib/pleroma/user.ex

@@ -747,7 +747,8 @@ defmodule Pleroma.User do
       :emoji,
       :accepts_chat_messages,
       :registration_reason,
-      :birthday
+      :birthday,
+      :language
     ])
     |> validate_required([:name, :nickname, :password, :password_confirmation])
     |> validate_confirmation(:password)

lib/pleroma/web/api_spec/operations/account_operation.ex

@@ -549,6 +549,11 @@ defmodule Pleroma.Web.ApiSpec.AccountOperation do
           nullable: true,
           description: "User's birthday",
           format: :date
+        },
+        language: %Schema{
+          type: :string,
+          nullable: true,
+          description: "User's preferred language for emails"
         }
       },
       example: %{

lib/pleroma/web/gettext.ex

@@ -35,6 +35,14 @@ defmodule Pleroma.Web.Gettext do
     |> String.replace("_", "-", global: true)
   end
 
+  def normalize_locale(locale) do
+    if is_binary(locale) do
+      String.replace(locale, "-", "_")
+    else
+      nil
+    end
+  end
+
   def supports_locale?(locale) do
     Pleroma.Web.Gettext
     |> Gettext.known_locales()

lib/pleroma/web/mastodon_api/controllers/account_controller.ex

@@ -221,7 +221,7 @@ defmodule Pleroma.Web.MastodonAPI.AccountController do
       # Note: param name is indeed :discoverable (not an error)
       |> Maps.put_if_present(:is_discoverable, params[:discoverable])
       |> Maps.put_if_present(:birthday, params[:birthday])
-      |> Maps.put_if_present(:language, params[:language])
+      |> Maps.put_if_present(:language, Pleroma.Web.Gettext.normalize_locale(params[:language]))
 
     # What happens here:
     #

lib/pleroma/web/plugs/set_locale_plug.ex

@@ -25,7 +25,7 @@ defmodule Pleroma.Web.Plugs.SetLocalePlug do
 
   defp normalize_language_codes(codes) do
     codes
-    |> Enum.map(fn code -> String.replace(code, "-", "_") end)
+    |> Enum.map(fn code -> Pleroma.Web.Gettext.normalize_locale(code) end)
   end
 
   defp extract_preferred_language(conn) do

lib/pleroma/web/twitter_api/twitter_api.ex

@@ -12,6 +12,8 @@ defmodule Pleroma.Web.TwitterAPI.TwitterAPI do
   alias Pleroma.UserInviteToken
 
   def register_user(params, opts \\ []) do
+    fallback_language = Gettext.get_locale()
+
     params =
       params
       |> Map.take([:email, :token, :password])
@@ -21,6 +23,10 @@ defmodule Pleroma.Web.TwitterAPI.TwitterAPI do
       |> Map.put(:password_confirmation, params[:password])
       |> Map.put(:registration_reason, params[:reason])
       |> Map.put(:birthday, params[:birthday])
+      |> Map.put(
+        :language,
+        Pleroma.Web.Gettext.normalize_locale(params[:language]) || fallback_language
+      )
 
     if Pleroma.Config.get([:instance, :registrations_open]) do
       create_user(params, opts)