Support connexion 3.0

[czchen]

connexion v3.0 has been released recently, and we found the following error when using it with prometheus_flask_exporter. Please help to update to support connexion v3.0.

> .../lib/python3.11/site-packages/prometheus_flask_exporter/__init__.py(718)func()
-> response = f(*args, **kwargs)
(Pdb) n
ModuleNotFoundError: No module named 'connexion.apis'
> .../lib/python3.11/site-packages/prometheus_flask_exporter/__init__.py(750)func()
-> response = self._response_converter(response)

[rycus86]

Thanks for reporting!
Would you have a minimal example to reproduce this on?

[rycus86]

I had a quick look at this but haven't figured out quickly how to test the latest Connexion with latest Flask, so an example to reproduce the problem on would be of great help here.