Change openapi docs to openapi v3

## What? Why? Who?

Replace the current openapi v2 docs with openapi v3 so that we can use the newer version for our future documentation.

## Acceptance Criteria

* Replace openapi v2 with v3 plugin.
* Update metadata accordingly.
* Generate yaml file instead of json file.
* Test if our current page can handle the yaml file.

## Scope

* qubic-http
