private String getApiId(Api api) {
        return getApiId(api.getOrganizationId(), api.getApiId(), api.getVersion());
    }
Generates a valid document ID for a api, used to index the api in ES.
@param api the api
@return an api key
gateway/engine/es/src/main/java/io/apiman/gateway/engine/es/EsRegistry.java