feat(subscription): Add support to estimate for a subscription in chargebee

[jagan-jaya]

Type of Change

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

Description

This pull request introduces support for fetching subscription estimates from Chargebee, alongside the existing subscription plans functionality. It adds new data structures, request/response types, and integration logic to handle the "Get Subscription Estimate" flow end-to-end. The changes span the domain models, interface types, and the Chargebee connector implementation.

Additional Changes

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

Motivation and Context

Closes #9055

How did you test it?

Compilation and PR checks are enough for now, as this is a new feature. Testing can be done after the external endpoint is added.

Checklist

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

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Changed Files

File	Status
crates/hyperswitch_domain_models/src/types.rs	66% smaller
crates/hyperswitch_interfaces/src/api/subscriptions.rs	47% smaller
crates/hyperswitch_interfaces/src/api/subscriptions_v2.rs	46% smaller
crates/hyperswitch_connectors/src/connectors/recurly.rs	41% smaller
crates/hyperswitch_connectors/src/default_implementations.rs	37% smaller
crates/hyperswitch_connectors/src/connectors/chargebee.rs	10% smaller
crates/hyperswitch_connectors/src/connectors/chargebee/transformers.rs	8% smaller
crates/hyperswitch_interfaces/src/types.rs	1% smaller
crates/hyperswitch_domain_models/src/router_data_v2/flow_common_types.rs	0% smaller
crates/hyperswitch_domain_models/src/router_flow_types/subscriptions.rs	0% smaller
crates/hyperswitch_domain_models/src/router_request_types/subscriptions.rs	0% smaller
crates/hyperswitch_domain_models/src/router_response_types/subscriptions.rs	0% smaller
crates/router/src/services/api.rs	0% smaller