feat(ai): add endpoints to chat with ai service

[apoorvdixit88]

Type of Change

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

Description

The PR does the following actions

• Adds endpoints to talk to ai services, particularly to n8n flow and embedded flow
• Introduces a feature flag to manage chat features across different envs

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 #8584

How did you test it?

curl to test this

curl --location 'http://localhost:8080/chat/ai/data' \
--header 'x-feature: integ-custom' \
--header 'Content-Type: application/json' \
--header 'Authorization: Bearer JWT' \
--data '{
            "message": "get count of failed payments"
    
}'

## 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/lib.rs	75% smaller
crates/router/src/routes/app.rs	3% smaller
crates/router/src/routes.rs	1% smaller
config/config.example.toml	Unsupported file format
config/deployments/env_specific.toml	Unsupported file format
config/development.toml	Unsupported file format
config/docker_compose.toml	Unsupported file format
crates/api_models/src/chat.rs	0% smaller
crates/api_models/src/events.rs	0% smaller
crates/api_models/src/events/chat.rs	0% smaller
crates/api_models/src/lib.rs	0% smaller
crates/common_utils/src/consts.rs	0% smaller
crates/common_utils/src/events.rs	0% smaller
crates/hyperswitch_domain_models/src/chat.rs	0% smaller
crates/hyperswitch_domain_models/src/lib.rs	0% smaller
crates/router/src/configs/secrets_transformers.rs	0% smaller
crates/router/src/configs/settings.rs	0% smaller
crates/router/src/configs/validations.rs	0% smaller
crates/router/src/core.rs	0% smaller
crates/router/src/core/chat.rs	0% smaller
crates/router/src/core/errors.rs	0% smaller
crates/router/src/core/errors/chat.rs	0% smaller
crates/router/src/routes/chat.rs	0% smaller
crates/router/src/routes/lock_utils.rs	0% smaller
crates/router_env/src/logger/types.rs	0% smaller
loadtest/config/development.toml	Unsupported file format

[SanchithHegde]

Would there be a situation where tenant ID might come into picture when calling the AI service?

[apoorvdixit88]

For now we are only considering merchant_id and giving result for merchant level data, if tenant id comes into picture we may have to make changes in the ai service as well to talk to the corresponding schema. Not sure, will depend on the tenant, how they want this service. This all can be as per the use case.

[SanchithHegde]

Should we consider logging only the identifiers (without the message or by masking the message)?
And should we consider adding metrics (indicating the number of chat requests made) as well, having identifiers as the metric attributes?

[apoorvdixit88]

logged the request with the masked message.

[SanchithHegde]

Nit: Should we consider having #[instrument] here as well?

[SanchithHegde]

Any specific reason for choosing this permission? If yes, should we consider explaining it in code comments?