Setting Up Gmail OAuth2 With Nodemailer and Google Cloud Platform (GCP)

Sending emails from applications now don evolve significantly from how e take dey be over the years. The normal way wey be username and password authentication for Gmail SMTP wey we been dey use before no really dey market again because of some kind security matters and Google's own restriction for apps wey dey considered "less secure". The latest way now wey secure pass na to use Gmail OAuth2 authentication, with another external emailing padi like Nodemailer. I been just run am for my portfol...