wormhole pairing appid flag day 2021-12-31

wormhole pairing appid flag day 2021-12-31

Wormhole pairing will start to provide an appid to wormhole on 2021-12-31.
An appid can't be provided now because Debian stable is going to ship a
older version of git-annex that does not provide an appid. Assumption is
that by 2021-12-31, this version of git-annex will be shipped in a Debian
stable release. If that turns out to not be the case, this change will need
to be cherry-picked into the git-annex in Debian stable, or its wormhole
pairing will break.

This commit was sponsored by Thomas Hochstein on Patreon.