Add request auto-retry options

[petermasking]

When scaling an application onto multiple servers we want to be fail safe. Currently we have a health check system that is used for monitoring the availability of nodes. In case one of the nodes is not healthy or doesn't respond, the gateway will stop using it. But when the gateway already forwarded a request to such a node, the request will fail.

As an improvement we need to add extends the gateway with a retry strategy. When a node has become unavailable, the gateway should look for an alternative node for the requested procedure and try it again on that node before it fails.