feat(swagger): Add OpenAPI v3 conversion to update_swagger.sh

[rahulsunil2]

This PR adds functionality to convert Swagger 2.0 (OpenAPI v2) to OpenAPI v3 using api-spec-converter in the update_swagger.sh script.

Description

This PR enhances the update_swagger.sh script by adding the following features:

1. Conversion of Swagger 2.0 (OpenAPI v2) to OpenAPI v3 using api-spec-converter.
2. Automatic creation of the output directory for OpenAPI v3 files if it doesn't exist.
3. Improved error handling and user feedback for the conversion process.
4. Instructions for installing api-spec-converter if it's not found on the system.

These changes improve the API documentation workflow by providing up-to-date OpenAPI v3 specifications alongside the existing Swagger 2.0 documentation.

References

• OpenAPI Initiative - Information about OpenAPI Specification
• api-spec-converter - Tool used for converting between API specification formats

Review Checklist

• [ ] I have clicked on "allow edits by maintainers".
• [ ] I have added documentation for new/changed functionality in this PR or in a PR to openfga.dev [Provide a link to any relevant PRs in the references section above]
• [ ] The correct base branch is being used, if not main
• [ ] I have added tests to validate that the change in functionality is working as expected
• [ ] I have tested the script with both existing and non-existing output directories
• [ ] I have verified that the script handles errors gracefully (e.g., when api-spec-converter is not installed)