chore(docker): added documentation

api/entrypoint.sh

@@ -1,6 +1,9 @@
 #!/bin/bash
 
+# wait for api database to come up
 host=dbapi; port=3306; n=120; i=0; while ! (echo > /dev/tcp/$host/$port) 2> /dev/null; do [[ $i -eq $n ]] && >&2 echo "$host:$port not up after $n seconds, exiting" && exit 1; echo "waiting for $host:$port to come up"; sleep 1; i=$((i+1)); done
+
+# wait for pdns api to come up
 host=nslord; port=8081; n=120; i=0; while ! (echo > /dev/tcp/$host/$port) 2> /dev/null; do [[ $i -eq $n ]] && >&2 echo "$host:$port not up after $n seconds, exiting" && exit 1; echo "waiting for $host:$port to come up"; sleep 1; i=$((i+1)); done
 
 python manage.py migrate