Add language settings for users, and translate titles to French

app/controllers/application_controller.rb

@@ -2,7 +2,7 @@ class ApplicationController < ActionController::Base
   include Authentication
   include Pundit::Authorization
 
-  before_action :set_title, :set_current_user
+  before_action :set_title, :set_current_user, :set_lang
   after_action :verify_authorized
 
   # Only allow modern browsers supporting webp images, web push, badges, import maps, CSS nesting, and CSS :has.
@@ -23,6 +23,10 @@ class ApplicationController < ActionController::Base
     @current_user = current_user
   end
 
+  def set_lang
+    I18n.locale = @current_user.lang if @current_user
+  end
+
   def user_not_authorized(exception)
     policy_name = exception.policy.class.to_s.underscore
 

app/controllers/users_controller.rb

@@ -55,6 +55,6 @@ class UsersController < ApplicationController
   end
 
   def user_params
-    params.expect(user: [ :username, :email_address, :password ])
+    params.expect(user: [ :username, :email_address, :lang, :password ])
   end
 end

app/lib/languages.rb

@@ -0,0 +1,3 @@
+module Languages
+  AVAILABLE_LANGUAGES = [ { id: "en", name: "English" }, { id: "fr", name: "French" } ]
+end

app/models/user.rb

@@ -5,6 +5,7 @@
 #  id              :integer          not null, primary key
 #  admin           :boolean          default(FALSE), not null
 #  email_address   :string           not null
+#  lang            :string           default("en")
 #  password_digest :string           not null
 #  username        :string
 #  created_at      :datetime         not null
@@ -22,4 +23,5 @@ class User < ApplicationRecord
   normalizes :email_address, with: ->(e) { e.strip.downcase }
 
   validates :username, presence: true, uniqueness: true
+  validates :lang, inclusion: { in: Languages::AVAILABLE_LANGUAGES.map { |lang| lang[:id] } }
 end

app/views/users/_form.html.slim

@@ -1,6 +1,7 @@
 = form_with model: user, method: method do |form|
   - if method == :patch
     h4 General settings
+  
   .row.mb-3
     .col
       .input-group
@@ -8,11 +9,20 @@
         .form-floating
           = form.text_field :username, autocomplete: "off", class: "form-control"
           = form.label :username, class: "required"
+
   .row.mb-3
     .col
       .form-floating
         = form.text_field :email_address, autocomplete: "off", class: "form-control"
         = form.label :email_address, class: "required"
+
+  .row.mb-3
+    .col
+      .form-floating
+        = form.select :lang, Languages::AVAILABLE_LANGUAGES.map { |lang| [ lang[:name], lang[:id] ] }, {}, class: "form-select"
+        = form.label :lang
+          | Language
+
   - if method == :post
     .row.mb-3
       .col
@@ -23,6 +33,7 @@
 
   - if method == :patch
     h4.mt-5 Change password
+
     = form_with model: user, method: method do |form|
       .row.mb-3
         .col