Updated dockerfile & added release workflow

.github/workflows/build-docker.yml

@@ -0,0 +1,47 @@
+name: Update docker image
+
+on:
+  workflow_dispatch:      # Trigger by hand from the UI
+  push:
+    branches:
+      - develop
+
+jobs:
+  build-and-release-docker-image:
+    name: Builds a dockerimage with the FEniCSx and its adapter
+    runs-on: ubuntu-latest
+    env:
+        docker_username: precice
+    steps:
+      - name: Get branch name
+        if: github.event_name != 'pull_request'
+        shell: bash
+        run: echo "branch=$(echo ${GITHUB_REF#refs/heads/} | tr / -)" >> $GITHUB_ENV    
+      - name: Checkout Repository
+        uses: actions/checkout@v2
+      - name: Set up Docker Buildx
+        uses: docker/setup-buildx-action@v1
+      - name: Login to DockerHub
+        uses: docker/login-action@v1
+        with:
+          username: ${{ env.docker_username }}
+          password: ${{ secrets.DOCKERHUB_TOKEN }}
+      - name: Build and export to Docker
+        uses: docker/build-push-action@v2
+        with:
+          load: true
+          file: "./tools/releasing/packaging/docker/Dockerfile"
+          tags: ${{ env.docker_username }}/fenicsx-adapter:${{ env.branch }},${{ env.docker_username }}/fenicsx-adapter:latest
+          build-args: |
+            branch=${{ env.branch }}
+      - name: Test adapter
+        run: |
+          docker run --rm ${{ env.docker_username }}/fenicsx-adapter:latest python3 -c "import fenicsxprecice"
+      - name: Build and push Dockerfile
+        uses: docker/build-push-action@v2
+        with:
+          push: true
+          file: "./tools/releasing/packaging/docker/Dockerfile"
+          tags: ${{ env.docker_username }}/fenicsx-adapter:${{ env.branch }},${{ env.docker_username }}/fenicsx-adapter:latest
+          build-args: |
+            branch=${{ env.branch }}

tools/releasing/packaging/docker/Dockerfile

@@ -1,11 +1,14 @@
-# Dockerfile to build a ubuntu image containing the installed Debian package of a release 
+# Dockerfile to build a ubuntu image containing the fenicsx-adapter. Based on the preCICE Python bindings
+# then we add the official package of FEniCSx and get the adapter.
 ARG branch=develop
 ARG from=precice/python-bindings:${branch}
 FROM $from
 
+# Install FEniCSx
 USER root
-# Installing necessary dependencies
-## TODO
+RUN add-apt-repository ppa:fenics-packages/fenics -y
+RUN apt update
+RUN apt install fenicsx -y
 
 USER precice
 
@@ -16,5 +19,5 @@ RUN python3 -m pip install --user --upgrade pip
 ARG CACHEBUST
 ARG branch=develop
 
-# Building fenics-adapter
+# Building fenicsx-adapter
 RUN python3 -m pip install --user git+https://github.com/precice/fenicsx-adapter.git@$branch