message: Update shadowbox docker node image to v12.16.3
diff: # See the License for the specific language governing permissions and
  # limitations under the License.
  -# See versions at https://hub.docker.com/_/node/
  -FROM node:8.15.0-alpine
  +# Newer node images have no valid content trust data.
  +# Pin the image node:12.16.3-alpine (linux/amd64) by hash.
  +# See versions at https://hub.docker.com/_/node?tab=tags&name=alpine
  +FROM node@sha256:12b2154fb459fa5f42c54771524609db041e7ef3465935d0ca82940d2d72669d
  # Versions can be found at https://github.com/Jigsaw-Code/outline-ss-server/releases
  ARG SS_VERSION=1.1.0
  # Save metadata on the software versions we are using.
  -LABEL shadowbox.node_version=8.15.0
  +LABEL shadowbox.node_version=12.16.3
  LABEL shadowbox.outline-ss-server_version="${SS_VERSION}"
  ARG GITHUB_RELEASE
  @@ -40,9 +42,8 @@ RUN mkdir bin && curl -SsL https://github.com/Jigsaw-Code/outline-ss-server/rele
  COPY third_party/prometheus/prometheus ./bin/
  COPY src/shadowbox/package.json .
  COPY yarn.lock .
  -# TODO: Replace with plain old "yarn" once the base image is fixed:
  -# https://github.com/nodejs/docker-node/pull/639
  -RUN /opt/yarn-v$YARN_VERSION/bin/yarn install --prod
  +
  +RUN yarn install --prod
  # Install management service
  COPY build/shadowbox/app app/
  