[16303] Add curl to Dockerfile (healthcheck)

Dockerfile

@@ -2,7 +2,7 @@ FROM adoptopenjdk/openjdk11:alpine-slim
 MAINTAINER MEDEVIT <office@medevit.at>
 ARG BRANCH=master
 
-RUN apk add --no-cache tzdata openvpn iptables sudo bash certbot openssl bind-tools
+RUN apk add --no-cache curl tzdata openvpn iptables sudo bash certbot openssl bind-tools
 ENV TZ=Europe/Zurich
 RUN addgroup elexis && adduser -S -u 1000 -G elexis -g "" -h /elexis elexis && \
     mkdir -p /opt/elexis-server && \