feat(connector): [Flexipay] add connector template code

[KiranKBR]

Type of Change

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

Description

Template code for Flexipay

Additional Changes

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

Motivation and Context

https://github.com/juspay/hyperswitch/issues/4664

How did you test it?

this is template code,so api testing not required

Checklist

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