/bin/check-availability can report availability incorrectly
For instance if the host URL is invalid it still says "instance available"
$ SIGNALBOOST_API_TOKEN=123 SIGNALBOOST_HOST_URL="not.a.real.url" ./bin/check-availability
--- checking if nextcloud instance available...
--- check #0
./bin/check-availability: line 25: [: !=: unary operator expected
--- instance available! continuing.
$ echo $?
0