systemd: load env file in gunicorn

allows to set georchestradatadir there for @fphg ;)

Author: landryb

env.example

@@ -3,3 +3,4 @@ CELERY_OPTS="-P solo -B -E -s workdir/celeybeat-schedule"
 CELERY_LOGLEVEL=INFO
 FLASK_APP=geordash
 FLASK_OPTS="-h 0.0.0.0 -p 5002"
+#georchestradatadir=/path/to/datadir

systemd/gaia-gunicorn.service.in

@@ -6,6 +6,7 @@ After=network.target
 Type=simple
 User=gunicorn
 Group=gaia
+EnvironmentFile=WORKDIR/env
 WorkingDirectory=WORKDIR
 ExecStart=gunicorn
 Restart=always