[SW]: Implementing OpenAPI Callback Support within Serverless Workflows

OpenAPI supports the functionality of long running processes called "Callbacks". See https://swagger.io/docs/specification/callbacks/

Supporting this within Kogito, would enable users to make use of this functionality to perform long running Request/Response operations enabled by the OpenAPI.

There are a few ways this could be implemented. A possible implementation would be:

• Allow Serverless Workflow Callback States to take a particular HTTP Response to resume the Workflow. (Currently only specif CloudEvents can be used to resume workflows.)
  • The HTTP Response would actually be a Request into the Workflow Server made by the OpenAPI service upon completion of the Long Running Process.
  • This implementation would allow for scaling down of the Orchestration Service while waiting for the OpenAPI to return.