Get Khoj Cloud Subscription URL via environment variable

src/khoj/interface/web/config.html

@@ -178,7 +178,7 @@
                 </div>
                 {% if not is_subscribed %}
                 <div class="card-action-row">
-                    <a class="card-button happy" href="https://buy.stripe.com/28ocQb7kb4iD0cEdQQ?email={{ username }}" target="_blank">
+                    <a class="card-button happy" href="{{ khoj_cloud_subscription_url }}?email={{ username }}" target="_blank">
                         Subscribe
                         <svg xmlns="http://www.w3.org/2000/svg" width="1em" height="1em" viewBox="0 0 24 24" fill="none" stroke="currentColor" stroke-width="2" stroke-linecap="round" stroke-linejoin="round"><path d="M5 12h14M12 5l7 7-7 7"></path></svg>
                     </a>

src/khoj/routers/api.py

@@ -782,7 +782,6 @@ async def unsubscribe(request: Request, email: str):
         customer_id = customer[0].id
         for subscription in stripe.Subscription.list(customer=customer_id):
             stripe.Subscription.modify(subscription.id, cancel_at_period_end=True)
-
         success = True
     else:
         success = False

src/khoj/routers/web_client.py

@@ -149,6 +149,7 @@ def config_page(request: Request):
             "user_photo": user_picture,
             "is_subscribed": user_is_subscribed,
             "days_to_renewal": days_to_renewal,
+            "khoj_cloud_subscription_url": os.getenv("KHOJ_CLOUD_SUBSCRIPTION_URL"),
         },
     )