Add simple CI

.gitlab-ci.yml

+image: jhipster/jhipster:v6.10.1
+
+variables:
+  MAVEN_OPTS: '-Dhttps.protocols=TLSv1.2 -Dmaven.repo.local=$CI_PROJECT_DIR/.m2/repository -Dorg.slf4j.simpleLogger.log.org.apache.maven.cli.transfer.Slf4jMavenTransferListener=WARN -Dorg.slf4j.simpleLogger.showDateTime=true -Djava.awt.headless=true'
+
+cache:
+  paths:
+    - .m2/repository
+
+stages:
+  - build
+
+maven-package:
+  stage: build
+  services:
+    - docker:19.03.8-dind
+  tags:
+    - docker
+  script:
+    - ./mvnw -B -Pprod,swagger verify
+    - cat target/jacoco-aggregate/index.html
+  artifacts:
+    reports:
+      junit: target/test-results/**/TEST-*.xml
+    paths:
+      - target/jacoco-aggregate
+    expire_in: 1 day
+  coverage: '/Total.*?([0-9]{1,3})%/'