refactor(relay): add trait based implementation for relay

[ShankarSinghC]

Type of Change

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

Description

This pr refactors the relay flow to add trait based implementation for it.

Changes made:-

1. relay_flow_decider decides the relay flow based on the relay types
2. Introduced RelayInterface trait that consists the methods required for different relay types
   a. validate_relay_request validates the relay requests for different type of relay types. It also provides default
   implementation, if a new relay type does not have specific type.
   b. get_domain_models to convert the relay request form api models to domain models
   c. process_relay that consists the core functionality for every relay type
   d. generate_response relay type specific response
3. Validate trait provides the generic validation. This trait can be implemented for any type, that requires validation.

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?

-> Make a relay payment

curl --location 'http://localhost:8080/relay' \
--header 'Content-Type: application/json' \
--header 'x-profile-id: pro_Zv50p4TBhOIRJFnynXL7' \
--header 'api-key: <api-key>' \
--data '{
    "connector_id": "mca_5dVmrsd0IwgQAsu3uiUo",
    "connector_resource_id": "pi_3Qs0CqEOqOywnAIx0QJ1vo67",
    "data": {
        "refund": {
            "amount": 1,
            "currency": "USD"
        }
    },
    "type": "refund"
}'

{
    "id": "relay_5nS1Mr5DHgWCkadiEVwY",
    "status": "success",
    "connector_resource_id": "pi_3Qs0CqEOqOywnAIx0QJ1vo67",
    "error": null,
    "connector_reference_id": "re_3Qs0CqEOqOywnAIx07ZIvgZ1",
    "connector_id": "mca_5dVmrsd0IwgQAsu3uiUo",
    "profile_id": "pro_Zv50p4TBhOIRJFnynXL7",
    "type": "refund",
    "data": {
        "refund": {
            "amount": 1,
            "currency": "USD",
            "reason": null
        }
    }
}

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]

Review changes with  

Changed Files

File	Status
crates/router/src/core/relay.rs	45% smaller
api-reference/openapi_spec.json	0% smaller
crates/api_models/src/relay.rs	0% smaller
crates/hyperswitch_domain_models/src/merchant_connector_account.rs	0% smaller
crates/hyperswitch_domain_models/src/relay.rs	0% smaller
crates/openapi/src/openapi.rs	0% smaller
crates/router/src/routes/relay.rs	0% smaller

[jarnura]

We should add Context here itself.