feat(routing): Contract based routing integration

[Sarthak1799]

Type of Change

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

Description

• Built an interface for Contract based routing
• Integrated Contract based routing with hyperswitch
• Built new APIs for contract routing config setup
• Refactored some existing dynamic routing code

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?

1. Enable Contract routing config

curl --location --request POST 'http://localhost:8080/account/sarthak2/business_profile/pro_YozTgS8HebvBlk0UaeWW/dynamic_routing/contracts/toggle?enable=dynamic_connector_selection' \
--header 'api-key: dev_1aD8YuFd6Ovanf3oOtAYobqI6qw4ZBRSfw6BgYbifWHpaopkisBtm8obNXkFbVJn' \
--header 'Content-Type: application/json' \
--data-raw '{
    "config": {
        "constants": [0.7,0.35],
        "time_scale": "day"
    },
    "label_info": [{
        "label": "stripe",
        "target_count": 10000,
        "incremental_count": 0,
        "target_time": 1780486655,
        "mca_id": "mca_5Mk0Qcum2tnbmKoyqeuL"
    }]
}'

Response -

{
    "id": "routing_FlQ49V71J8ZCXEwPzFy9",
    "profile_id": "pro_YozTgS8HebvBlk0UaeWW",
    "name": "Contract based dynamic routing algorithm",
    "kind": "dynamic",
    "description": "",
    "created_at": 1734009361,
    "modified_at": 1734009361,
    "algorithm_for": "payment"
}

2. Set Volume split for dynamic routing

curl --location --request POST 'http://localhost:8080/account/sarthak2/business_profile/pro_YozTgS8HebvBlk0UaeWW/dynamic_routing/set_volume_split?split=80' \
--header 'api-key: dev_1aD8YuFd6Ovanf3oOtAYobqI6qw4ZBRSfw6BgYbifWHpaopkisBtm8obNXkFbVJn'

3. Create a Payment
   Metrics Population post payment -

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/external_services/build.rs	35% smaller
crates/api_models/src/events/routing.rs	35% smaller
crates/router/src/routes/app.rs	26% smaller
crates/storage_impl/src/redis/pub_sub.rs	23% smaller
crates/router/src/core/payments/routing.rs	17% smaller
crates/api_models/src/routing.rs	12% smaller
crates/router/src/core/payments/operations/payment_response.rs	3% smaller
crates/storage_impl/src/redis/cache.rs	3% smaller
crates/router/src/core/routing.rs	2% smaller
crates/external_services/src/grpc_client/dynamic_routing.rs	1% smaller
api-reference/openapi_spec.json	1% smaller
.github/CODEOWNERS	Unsupported file format
crates/external_services/src/grpc_client/dynamic_routing/contract_routing_client.rs	0% smaller
crates/external_services/src/grpc_client/dynamic_routing/elimination_based_client.rs	0% smaller
crates/openapi/src/openapi.rs	0% smaller
crates/openapi/src/routes/routing.rs	0% smaller
crates/router/src/core/errors.rs	0% smaller
crates/router/src/core/metrics.rs	0% smaller
crates/router/src/core/payments.rs	0% smaller
crates/router/src/core/routing/helpers.rs	0% smaller
crates/router/src/routes/metrics/bg_metrics_collector.rs	0% smaller
crates/router/src/routes/routing.rs	0% smaller
proto/contract_routing.proto	Unsupported file format

[NishantJoshi00]

Looks good, some questions:

1. Is this enabled by default?
2. Have you tested if this works for a contract?
3. Where are the state for this being stored?
4. Where is the flow this is being called?
5. Are any interactions with dynamic routing service in the critical path (if so, how do we handle network failures)
6. I was able to see some caching changes, will this affect the state management for managing contract.

I think its imperative to follow micro PR model to avoid such confusions;

1. it becomes difficult to follow the code changes.
2. Such massive changes can hide bugs which are difficult to find due to its sheer size.

[Sarthak1799]

• We have to enable contract based routing using setup APIs introduced in this PR
• have tested the flow locally
• The actual config is stored in routing_algorithm with it's ref stored in profile, like all other DR algorithms
• Similar to other routing types, this will be called in the payment flow, if the contract based algo is enabled.
• In case of Dynamic routing failure, the list of eligible of connectors are defaulted to the list from static routing
• The caching changes here are to make the caching code generic to all categories of Dynamic routing (SR, ER, Contracts) and making use of specific functions from redis interface (like get_or_populate_in_memory)
  cc: @Chethan-rao

Agreed on the micro PR model @NishantJoshi00, had thought about breaking up in several PRs but much of the reviews were already completed at the time.