github: define dockerhub workflow

* build and push Docker Images to DockerHub

.github/workflows/dockerhub.yml

@@ -0,0 +1,41 @@
+---
+name: dockerhub
+
+on:
+  push:
+    branches:
+      - '5.*'
+
+jobs:
+  pre-docker:
+    runs-on: ubuntu-latest
+    steps:
+      - uses: actions/checkout@v2
+      - id: set-matrix
+        run: |
+          sudo apt-get install jq
+          echo "::set-output name=matrix::$(bash get-all-dist.sh)"
+    outputs:
+      matrix: ${{ steps.set-matrix.outputs.matrix }}
+  docker:
+    needs: pre-docker
+    runs-on: ubuntu-latest
+    strategy:
+      matrix:
+        dist: ${{fromJson(needs.pre-docker.outputs.matrix)}}
+    steps:
+      - name: Set up QEMU
+        uses: docker/setup-qemu-action@v2
+      - name: Set up Docker Buildx
+        uses: docker/setup-buildx-action@v2
+      - name: Login to DockerHub
+        uses: docker/login-action@v2
+        with:
+          username: ${{ secrets.DOCKERHUB_USERNAME }}
+          password: ${{ secrets.DOCKERHUB_TOKEN }}
+      - name: Build and push
+        uses: docker/build-push-action@v3
+        with:
+          context: "{{defaultContext}}:${{ matrix.dist }}"
+          push: true
+          tags: kamailio/kamailio:${{ github.ref_name }}-${{ matrix.dist }}

get-all-dist.sh

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+#!/bin/bash
+find . -name Dockerfile -exec dirname {} \; | jq -R . | sed 's#./##g' | jq -cs .