Layer2 config for retail domain

[rajaneeshk90]

Description

Networks created using Beckn Onix use two layers of configurations for the request and response validation in a transaction.

As part of this PR, an example layer 2 configuration for the retail domain is created.

Changes

1. A new OpenAPI document "api/l2-config/localretail_shopping_1.1.0.yaml" is created.
2. A postman collection, "api/l2-config/postman-collection-test-cases/Retail-with-layer2.postman_collection.json", is created to test the network rules added in the layer 2 config.

Tools needed to test this PR

Postman Desktop or Web Application.

How to test

1. Import the postman collection "api/l2-config/postman-collection-test-cases/Retail-with-layer2.postman_collection.json" into the postman application.
2. The postman collection contains ~50 requests, these requests are named in a way that clearly conveys their intended purpose.
3. Send the requests to verify that the added rule are working as expected.

Notes

This is an example configuration for a Layer 2 network. Network facilitators setting up a new network may use this as a reference. Adjustments may be necessary to suit specific network requirements and conditions.