Routing operation exposed via Event Bus

Vert.x API Contract allows to define operations that are consumed by event bus handlers. This functionality comes from https://vertx.io/docs/vertx-web-api-service/java/. This issue is about defining and implementing this new functionality.

Start by reading the Vert.x API Contract and vertx-web-api-service documentation linked in the issue, then inspect how this HTTP server currently routes requests using OpenAPI specs. The work is done when operations can be defined and implemented as event bus handlers, with the integration behavior made clear and verified.

Written by the indexing model from the issue text.