How to build a register user flow in Next.js 15 (frontend, backend, database, email)

This is part 3 of the series on building an auth system from scratch. Today: the register user flow. By the end you will have a working signup page, a server endpoint, a users table, and a verification email getting delivered. The flow, end to end Here is what happens when a user hits "Create account": +-------+ +------------+ +-----------+ +--------+ |Browser| POST | Next.js | INSERT| Postgres | SEND |Resend | | |------->|/api/ |------>| users |----->| | | | |auth/ | | (verify=F| | | | | And th