Implement updateSubscription feature and refactor billing services

This commit introduces the updateSubscription method to the BillingStrategyProviderService, ensuring that subscriptions can be updated within the billing core. Additionally, a refactor has been applied to the BillingGatewayFactoryService and stripe-billing-strategy.service to improve error handling and the robustness of subscription updates. Logging in the webhook route has been adjusted for clarity and the data model has been enhanced.

packages/features/accounts/src/server/services/delete-personal-account.service.ts

@@ -94,14 +94,13 @@ export class DeletePersonalAccountService {
     productName: string;
   }) {
     const { renderAccountDeleteEmail } = await import('@kit/email-templates');
-    const mailer = new Mailer();
 
     const html = renderAccountDeleteEmail({
       userDisplayName: params.userDisplayName,
       productName: params.productName,
     });
 
-    await mailer.sendEmail({
+    await Mailer.sendEmail({
       to: params.userEmail,
       from: params.fromEmail,
       subject: 'Account Deletion Request',