pics.2bit.challenge.join

The author taking part in a challenge. Joining is how a challenge comes to be offered wherever the author posts - nobody is signed up for a challenge they didn't join - and it's public, like a follow, so a challenge can show who's taking part before anyone has entered. Entering a prompt joins too. One join per person per challenge is enforced by this app's AppView rather than the record key: its write path won't write a second, and where another client leaves several, they count once. Leaving deletes the join and nothing else - entries already made stay.