feat: mysql-bkup v2 on bkupkit

MysQL backup and restore built on the shared bkupkit core:
streaming end to end, with no dump held in memory or written to
local disk.

examples/docker-compose.yaml

@@ -1,4 +1,3 @@
-version: "3"
 services:
   mysql-bkup:
     image: jkaninda/mysql-bkup
@@ -9,5 +8,5 @@ services:
     environment:
       - DB_PORT=3306
       - DB_HOST=mysql
-      - DB_USERNAME=userName
+      - DB_USER=userName
       - DB_PASSWORD=${DB_PASSWORD}