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.

.github/workflows/build.yml

@@ -10,19 +10,19 @@ jobs:
     steps:
       -
         name: Set up QEMU
-        uses: docker/setup-qemu-action@v3
+        uses: docker/setup-qemu-action@v4
       -
         name: Set up Docker Buildx
-        uses: docker/setup-buildx-action@v3
+        uses: docker/setup-buildx-action@v4
       -
         name: Login to DockerHub
-        uses: docker/login-action@v3
+        uses: docker/login-action@v4
         with:
           username: ${{ secrets.DOCKERHUB_USERNAME }}
           password: ${{ secrets.DOCKERHUB_TOKEN }}
       -
         name: Build and push
-        uses: docker/build-push-action@v3
+        uses: docker/build-push-action@v7
         with:
           push: true
           file: "./Dockerfile"
@@ -30,5 +30,5 @@ jobs:
           build-args: |
             appVersion=nightly
           tags: |
-            "${{vars.BUILDKIT_IMAGE}}:nightly"
+            "${{ vars.BUILDKIT_IMAGE || 'jkaninda/mysql-bkup' }}:nightly"