Add JWT authentication to the Manager app

Gemfile

@@ -37,6 +37,7 @@ gem 'strong_migrations'
 gem 'tailwindcss-rails'
 gem 'turbo-rails'
 gem 'tzinfo-data', platforms: %i[mingw mswin x64_mingw jruby]
+gem 'jwt'
 
 group :development, :test do
   gem 'debug', platforms: %i[mri mingw x64_mingw]

Gemfile.lock

@@ -167,6 +167,8 @@ GEM
     json (2.9.1)
     json-schema (5.0.1)
       addressable (~> 2.8)
+    jwt (2.10.1)
+      base64
     kaminari (1.2.2)
       activesupport (>= 4.1.0)
       kaminari-actionview (= 1.2.2)
@@ -466,6 +468,7 @@ DEPENDENCIES
   groupdate
   httparty
   importmap-rails
+  jwt
   kaminari
   lograge
   oj

app/models/user.rb

@@ -99,6 +99,20 @@ class User < ApplicationRecord
     end
   end
 
+  # Generates a secure token for cross-application authentication with the subscription app
+  # @return [String] JWT token containing user identity information
+  def generate_subscription_token
+    payload = {
+      user_id: id,
+      email: email,
+      exp: 30.minutes.from_now.to_i
+    }
+
+    secret_key = ENV['JWT_SECRET_KEY']
+
+    JWT.encode(payload, secret_key, 'HS256')
+  end
+
   private
 
   def create_api_key

app/views/settings/subscriptions/index.html.erb

@@ -16,13 +16,13 @@
             Your subscription will be valid for the next <span class="text-accent"><%= 365 %> days</span> and will be <span class="text-accent"><%= current_user.active? ? 'renewed automatically' : 'renewed manually' %></span>.
           </p>
 
-          <%= link_to 'Manage subscription', '#', class: 'btn btn-primary my-4' %>
+          <%= link_to 'Manage subscription', "#{ENV['SUBSCRIPTION_URL']}/auth/dawarich?token=#{current_user.generate_subscription_token}", class: 'btn btn-primary my-4' %>
         <% else %>
           <p class="py-6">
             You are currently not subscribed to Dawarich. How about we fix that?
           </p>
 
-          <%= link_to 'Manage subscription', '#', class: 'btn btn-primary my-4' %>
+          <%= link_to 'Manage subscription', "#{ENV['SUBSCRIPTION_URL']}/auth/dawarich?token=#{current_user.generate_subscription_token}", class: 'btn btn-primary my-4' %>
         <% end %>
       </div>
     </div>