Guidelines for asynchronous response in callback

[rartych]

Problem description
Currently there are guidelines for event management in 12. Subscription, Notification & Event. However callback can be used for asynchronous response as in Population Density API where the response may need more time for computation and can contain large data chunk.

Possible evolution
Guidelines for asynchronous response in callback should be added.

Alternative solutions

• Include asynchronous response in the 12. Subscription, Notification & Event

• Leave the decision for subprojects.

Additional context
https://openapispec.com/docs/how/how-does-openapi-support-asynchronous-apis/