Add locale param to sign-up API (#9747)

Fix #9627

app/controllers/api/v1/accounts_controller.rb

@@ -76,7 +76,7 @@ class Api::V1::AccountsController < Api::BaseController
   end
 
   def account_params
-    params.permit(:username, :email, :password, :agreement)
+    params.permit(:username, :email, :password, :agreement, :locale)
   end
 
   def check_enabled_registrations

app/services/app_sign_up_service.rb

@@ -4,7 +4,7 @@ class AppSignUpService < BaseService
   def call(app, params)
     return unless allowed_registrations?
 
-    user_params    = params.slice(:email, :password, :agreement)
+    user_params    = params.slice(:email, :password, :agreement, :locale)
     account_params = params.slice(:username)
     user           = User.create!(user_params.merge(created_by_application: app, password_confirmation: user_params[:password], account_attributes: account_params))