refactor(payment_methods): update payment method db operations to include multi-key validation

[Chethan-rao]

Type of Change

• [ ] Bugfix
• [ ] New feature
• [ ] Enhancement
• [x] Refactoring
• [ ] Dependency updates
• [ ] Documentation
• [ ] CI/CD

Description

Currently, payment method apis like retrieve, update and delete are happening in db based on payment_method_id only. This PR refactors it to include all 3 keys (merchant_id, customer_id and payment_method_id) for validation in retrieving, updating and deleting payment method.

Additional Changes

• [x] This PR modifies the API contract
• [ ] This PR modifies the database schema
• [ ] This PR modifies application configuration/environment variables

Motivation and Context

How did you test it?

This PR can be tested in the same way as https://github.com/juspay/hyperswitch/pull/3146.

Checklist

• [x] I formatted the code cargo +nightly fmt --all
• [x] I addressed lints thrown by cargo clippy
• [x] I reviewed the submitted code
• [ ] I added unit tests for my changes where possible
• [ ] I added a CHANGELOG entry if applicable