private String getClientIndex(String orgId, String clientId, String version) {
        return "CLIENT::" + orgId + "|" + clientId + "|" + version; //$NON-NLS-1$ //$NON-NLS-2$ //$NON-NLS-3$
    }
Generates an in-memory key for an client, used to index the client for later quick
retrieval.
@param client an client
@return a client key
gateway/engine/core/src/main/java/io/apiman/gateway/engine/impl/InMemoryRegistry.java