feat(router): add core changes for external authentication flow through unified_authentication_service

[sai-harsha-vardhan]

Type of Change

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

Description

add core changes for external authentication flow through unified_authentication_service

Additional Changes

• 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?

Compiler guided - Core changes alone done, can be tested after connector related changes are done

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

[semanticdiff-com]

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Changed Files

File	Status
crates/router/src/routes/payments.rs	89% smaller
crates/router/src/types.rs	73% smaller
crates/router/src/core/payments.rs	57% smaller
crates/hyperswitch_connectors/src/connectors/unified_authentication_service.rs	47% smaller
crates/hyperswitch_connectors/src/connectors/unified_authentication_service/transformers.rs	40% smaller
crates/router/src/core/payments/connector_integration_v2_impls.rs	36% smaller
crates/hyperswitch_domain_models/src/types.rs	30% smaller
crates/hyperswitch_domain_models/src/router_request_types/unified_authentication_service.rs	18% smaller
crates/hyperswitch_interfaces/src/types.rs	15% smaller
crates/hyperswitch_interfaces/src/api.rs	12% smaller
crates/router/src/core/payments/operations/payment_confirm.rs	11% smaller
crates/router/src/core/unified_authentication_service/types.rs	8% smaller
crates/router/src/core/unified_authentication_service.rs	7% smaller
crates/router/src/core/payments/flows.rs	5% smaller
crates/hyperswitch_connectors/src/default_implementations.rs	2% smaller
crates/hyperswitch_domain_models/src/router_flow_types/unified_authentication_service.rs	0% smaller
crates/router/src/core/payments/helpers.rs	0% smaller
crates/router/src/core/payments/operations.rs	0% smaller
crates/router/src/core/unified_authentication_service/transformers.rs	0% smaller
crates/router/src/core/unified_authentication_service/utils.rs	Unsupported file format