protected String getApiIndex(Api api) {
        return getApiIndex(api.getOrganizationId(), api.getApiId(), api.getVersion());
    }
Generates an in-memory key for an api, used to index the client for later quick
retrieval.
@param api an api
@return a api key
gateway/engine/core/src/main/java/io/apiman/gateway/engine/impl/InMemoryRegistry.java