Add service to generate a key that would map to the current instance

background: in order to obtain a hashcode that maps to the current node, the way to go is to generate random keys and pass them to the hashing algorithm until the hash for one of them will match the node. This JIRA is about creating an async service to do that, so that the calling thread won't be blocked while this happens.

-------------------- from an email discussion

What about adding a service to asynchronously generate and pool a number
of ids that map to a certain node (in our use case same node)?

Advantage would be that the calling thread won't have to wait until we
determine an appropriate value.

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