Replace akka-http

akka is not open source anymore so we won't benefit from updates.
When the opportunity comes, we should move to http4s which will besides have a better integration with the rest of the stack.

Note that we don't only use akka-http as a http server, we also use it:
* As a http client
* We also use it (ex: Uri) in our rdf module
* Reassess ScalaTest and MUnit to see which fits better with the new solution