Add Subscriptions

[MikeAlhayek]

Fixes #11

Tasks:

• [x] Implement the core Subscriptions feature.
• [x] Develop the Subscription for Tenants functionality.
• [x] Integrate support for Multiple Payment Providers.
• [x] Add Stripe Integration.
• [x] Implement the Pay-Later payment provider.
• [x] Store the SubscriptionId in a cookie for retrieval and do not create new session on first GET request.
• [x] Add a ReCaptcha on the very first step.
• [ ] Design the Admin UI for subscription management.
• [ ] Create Admin Dashboard Widgets for subscription summaries.
• [ ] Build the User Subscription Management interface.
• [ ] Add workflow events to allow users to build custom workflows.
• [ ] Enhance the confirmation step to include more details, such as new site admin info (excluding passwords), subscription information, payment amount, next payment date, and instructions for managing the subscription.
• [x] Refactor the SubscriptionPart class by extracting non-subscription-related properties and moving them to a new ProductPart class. This will provide better flexibility for future development, such as handling services that do not require a subscription.

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This pull request has merge conflicts. Please resolve those before requesting a review.

[github-actions[bot]]

This pull request has merge conflicts. Please resolve those before requesting a review.

[github-actions[bot]]

This pull request has merge conflicts. Please resolve those before requesting a review.

[github-actions[bot]]

This pull request has merge conflicts. Please resolve those before requesting a review.

[github-actions[bot]]

This pull request has merge conflicts. Please resolve those before requesting a review.