consider moving to fast-api to support newer python versions

[nvdk]

As discussed on rocket chat , meinheld webserver is no longer supported on newer python versions.

The maintainer of our base docker image seems to suggest moving to fast api instead of flask. This is not a drop in solution for flask, but for our usage it could be (we don't use many flask builtins). Some information on dockerizing fast api can be found here https://fastapi.tiangolo.com/deployment/docker/#dockerfile