Add Generic HttpClientFactory Service

most of this is already implemented in https://github.com/wcm-io/wcm-io-caravan/tree/master/io/http/src/main/java/io/wcm/caravan/io/http/httpclient
it supports both synch and asynch http client.

we have to refactor this into a separate project in wcm.io caravan or move this part to wcm.io.
additionally we should support to load certificate/trust stores from the repository via sling, additionally to loading them from the filesystem to allow flexible deployment via packages.

is it possible to use it a single dependency in the project already or do i have to include anything else from caravan?

this should provided what is required - in a dedicated bundle:
https://github.com/wcm-io/wcm-io-caravan/tree/master/commons/httpclient

the 4 dependency bundles have to be deployed as well.

ok, thank you. this worked well.