Verify OpenAPI 3 specification is up-to-date in CI pipeline

Overview

Add a CI job to verify that the generated OpenAPI 3 specification is up-to-date in the repository. This ensures that any changes to the API are reflected in the OpenAPI specification before merging.

Implementation plan

• Add a CI job that runs the OpenAPI generator
• Compare the generated specification with the stored version in the repository
• Fail the job if there are any differences between the generated and stored versions
• Provide clear error messages indicating that the specification needs to be regenerated
• This should be encapsulated in a single rake task.

Note: An existing job does this for OpenAPI 2.0 and is available in a rake task.