Because we have incompatibilites and linkage errors with Apache HTTP
Client in WIldfly I did the following changes:
* I created an Apache HTTP Client "connections provider" module which
outgoing server connections now use.
* This provider is configured in keycloak-server.json and documentation
is in docbook for it.
* Outgoing HTTP requests no longer use Resteasy ClientRequest.
Things to do:
* We need stress tests for backchannel logouts and other
ResourceAdminManager requests. Broker and admin console. Now that an
HttpClient instance is only created once at boot time instead of per
request, we need to make absolutely sure connections are being cleaned up.
* I need to test backchannel and ResourceAdminManager requests with
JBoss, a division of Red Hat