update migration guide

pages/sessions/migrate-lucia-v3.md

@@ -6,8 +6,6 @@ title: "Migrate from Lucia v3"
 
 Because Lucia v3 is lightweight and relatively low-level, migrating your project shouldn't take long. Moreover, most of your knowledge will still be very useful. No database migrations are necessary.
 
-The one change to how sessions work is that session tokens are now hashed before storage. The pre-hash token is the client-assigned session ID and the hash is the internal session ID. The easiest option would be to purge all existing sessions, but if you want keep existing sessions, SHA-256 and hex-encode the session IDs stored in the database. Or, you can skip the hashing altogether. Hashing is a good measure against database leaks, but not absolutely necessary.
-
 APIs on sessions are covered in the [Basic session API](/sessions/basic-api) page.
 
 - `Lucia.createSession()` => `generateSessionToken()` and `createSession()`
@@ -19,4 +17,21 @@ APIs on cookies are covered in the [Session cookies](/sessions/cookies) page.
 - `Lucia.createSessionCookie()` => `setSessionTokenCookie()`
 - `Lucia.createBlankSessionCookie()` => `deleteSessionTokenCookie()`
 
+The one change to how sessions work is that session tokens are now hashed before storage. The pre-hash token is the client-assigned session ID and the hash is the internal session ID. The easiest option would be to purge all existing sessions, but if you want keep existing sessions, SHA-256 and hex-encode the session IDs stored in the database. Or, you can skip the hashing altogether. Hashing is a good measure against database leaks, but not absolutely necessary.
+
+```ts
+export function createSession(userId: number): Session {
+	const bytes = new Uint8Array(20);
+	crypto.getRandomValues(bytes);
+	const sessionId = encodeBase32LowerCaseNoPadding(bytes);
+	// Insert session into database.
+	return session;
+}
+
+export function validateSessionToken(sessionId: string): SessionValidationResult {
+	// Get and validate session
+	return { session, user };
+}
+```
+
 If you need help or have any questions, please ask them on [Discord](https://discord.com/invite/PwrK3kpVR3) or on [GitHub discussions](https://github.com/lucia-auth/lucia/discussions).