https://cloud.google.com/iot/docs/how-tos/http-bridge
for google rest api ( https ) you need:
google_long_ca.pem certificate (can and full certificate)
https://cloud.google.com/iot/docs/how-tos/mqtt-bridge#using_a_long-term_mqtt_domain
and you need to calculate your JWT key
load certificate in module
create post header
post json data {“binary_data”:“SGVsbG8gZnJvbSBBenVyZSBTcGhlcmU=”} // Base64
easy … tested with different modules…