feat(tools): Add Stripe integration for billing and payments

[vakrahul]

Summary

This PR implements the requested stripe_tool to allow agents to interact with billing data. It has been significantly expanded to cover the full customer and subscription lifecycle based on review feedback.

Changes

• Expanded Stripe Tool: Now supports full lifecycle management (15+ functions).
  • Customer: create, update, get_by_email, get_by_id, list
  • Subscription: create, update, cancel, list, get_status
  • Invoice: list, retrieve, pay
  • Checkout & Payments: create_checkout_session, create_payment_link, list_payment_intents
  • Webhooks: verify_webhook_signature
• Configuration: Added STRIPE_API_KEY to credential management and registered new tools.
• Testing: Added comprehensive mock tests covering all new workflows.

Testing

• Ran pytest tools/tests/tools/test_stripe_tool.py
• Result: 7 passed (Verified locally with unittest.mock to ensure logic correctness without API calls).

Related Issue

#2860

[vakrahul]

hi @RichardTang-Aden

• Expanded stripe_tool: Significantly updated the module to support the full billing lifecycle (15+ functions):
  • Customers: create, update, list, and get (Full CRUD).
  • Subscriptions: create, update, cancel, and list (SaaS lifecycle).
  • Invoices: list, retrieve, and pay functionality.
  • Checkout & Webhooks: Added create_checkout_session and verify_webhook_signature.
• Credential Management: Updated STRIPE_API_KEY in credentials/stripe.py to support the new write-access tools.
• Dependencies: Added stripe to pyproject.toml.
• Testing: Expanded unit tests using unittest.mock to verify the new create/update/cancel logic.

Testing

I verified these changes using both manual checks and automated unit tests:

• Unit tests pass (pytest tools/tests/tools/test_stripe_tool.py) - Result: 7 passed
• Lint passes (make check)
• Manual testing performed: Verified create_payment_link generated a valid URL using a test key.

Checklist

• My code follows the project's style guidelines
• I have performed a self-review of my code
• I have commented my code, particularly in hard-to-understand areas
• I have made corresponding changes to the documentation (tools/src/aden_tools/tools/stripe_tool/README.md)
• My changes generate no new warnings
• I have added tests that prove my fix is effective or that my feature works
• New and existing unit tests pass locally with my changes

[vakrahul]

@RichardTang-Aden please review it