Migrate Beckn Core Protocol Specification from OpenAPI 3.0 to 3.1: Release core spec version 1.1.1

**Background**

The Beckn Core Protocol is currently specified using OpenAPI version 3.0. To leverage the latest features, improvements, and compliance enhancements in OpenAPI 3.1, there is a need to update the protocol specification.
Furthermore, the protocol specification version release is tagged as 1.1.0 but yaml file still has 1.0.0 which needs to be fixed.
The current release of version 1.1.1 should automatically fix this bug also.

**Objectives**

- Upgrade Specification: Update the Beckn Core Protocol YAML files to be compliant with OpenAPI 3.1.
- Validate Compatibility: Ensure that all existing API definitions are compatible with OpenAPI 3.1 syntax and semantics.
- Documentation and Examples: Update accompanying documentation and examples to reflect changes made during the migration.
- Tooling and Integration: Verify that all related tooling (e.g., code generators, validators, linters) support and work seamlessly with OpenAPI 3.1.

**Tasks**

- Review Changes in OpenAPI 3.1:
- Understand key differences between OpenAPI 3.0 and 3.1.
- Identify features in 3.1 that are relevant to the Beckn Core Protocol.
- Update YAML Files:
- Modify existing OpenAPI 3.0 YAML files to conform to OpenAPI 3.1 standards.
- Ensure all endpoints, schemas, and components are correctly defined.
- Testing and Validation:
- Use OpenAPI 3.1 validation tools to verify the updated specifications.
- Perform integration tests to ensure no regressions or issues arise from the migration.
- Update Documentation:
- Revise documentation to reflect changes in the specification.
- Provide updated examples and usage guidelines for developers.
- Coordinate with Stakeholders:
- Communicate with developers, integrators, and other stakeholders regarding the migration.
- Offer support and guidance for any issues arising from the update.

**Expected Outcomes**

- A fully migrated Beckn Core Protocol specification compliant with OpenAPI 3.1.
- Updated documentation and examples that align with the new specification.
- Enhanced compatibility with modern tooling and improved protocol features.

**References**

- [OpenAPI 3.1 Specification](https://github.com/OAI/OpenAPI-Specification)
- Migration Guide from OpenAPI 3.0 to 3.1