Add graphviz to docker image (#1623)

This fixes the usage of the plantuml plugin inside of a docker
container.

gradle/changelog/add_missing_graphviz.yaml

@@ -0,0 +1,2 @@
+- type: fixed
+  description: Missing graphviz in docker image ([#1623](https://github.com/scm-manager/scm-manager/pull/1623))

scm-packaging/docker/Dockerfile

@@ -29,7 +29,8 @@ ENV CACHE_DIR=/var/cache/scm/work
 COPY . /
 
 RUN set -x \
- && apk add --no-cache ttf-dejavu mercurial bash ca-certificates \
+ # ttf-dejavu graphviz are required for the plantuml plugin
+ && apk add --no-cache ttf-dejavu graphviz mercurial bash ca-certificates \
  && addgroup -S -g 1000 scm \
  && adduser -S -s /bin/false -G scm -h ${SCM_HOME} -D -H -u 1000 scm \
  && mkdir -p ${SCM_HOME} ${CACHE_DIR} \