`POST /link/confirm` forwards a one-time link code to the plugin and hands back
what it says. Everything before it was the website reading what the game had
already told us; this is the website asking the game a question only the game can
answer.
**It is still a forwarder and holds no authority of its own.** It does not mint
codes, does not store them, does not know what a website user is, and cannot tell
a good code from a bad one. Putting the code table here would give the sidecar a
credential and an opinion, and D2 and the bridge principles say it has neither.
**A refused code is a 200.** `link.ok` and `link.error` are both answers, and the
website has to tell "that code is wrong" from "the game never replied" to say the
right thing to a player. The two transport failures keep the codes `respond`
already gives them: 503 when the game is down, 504 when it is up and silent.
`usable_code` is split out and tested because its two rejections are easy to get
subtly wrong. It trims BEFORE it measures: a player pasting a code out of game
chat brings whitespace with it, a field of nothing but spaces is empty rather
than four characters long, and the length bound belongs on the trimmed value.
Co-Authored-By: Claude Opus 5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_016wDDVXWMDz82WqE1i969r4
