Backup and restore process (#641)

* Make db dump more modular

* Add basic backup and restore scripts

* Exit on error

* Exit with error code in case of missing file

* Determine volumes location programatically

A bit hacky, maybe there's a better way - open for suggestions!

* gzip database dump

* Restore database

* Fail on pipe errors

* Encrypt backup using gpg; improve log messages

* Ensure database container is up during dump and import

* Restore volumes

backup.sh

@@ -52,7 +52,7 @@ esac
 volumes_dir=/var/lib/docker/volumes
 backup_dir="$volumes_dir/backup_datadir"
 filename="backup.tar.gz"
-dumpname="postgres.sql"
+dumpname="postgres.sql.gz"
 
 if [ "$BACKUP_TIMESTAMP" == true ]; then
   timestamp=$(date "+%Y%m%d-%H%M%S")
@@ -66,9 +66,14 @@ dbdump_path="$backup_dir/_data/${dumpname}"
 cd "$BTCPAY_BASE_DIRECTORY/btcpayserver-docker"
 . helpers.sh
 
+# ensure backup dir exists
+if [ ! -d "$backup_dir" ]; then
+    docker volume create backup_datadir
+fi
+
 # dump database
 echo "Dumping database …"
-btcpay_dump_db $dumpname
+btcpay_dump_db $dbdump_path
 
 if [[ "$1" == "--only-db" ]]; then
     tar -cvzf $backup_path $dbdump_path