RM-3487: add gitlab CI file

Author: jann0k

.gitlab-ci.yml

@@ -0,0 +1,19 @@
+stages:
+  - publish
+
+publish:
+  stage: publish
+  image: maven:3.8.8-eclipse-temurin-17
+  script: mvn deploy -s $MAVEN_SETTINGS
+  cache:
+    key: "$CI_COMMIT_REF_NAME"
+    paths:
+      - .m2/repository
+  rules:
+    - if: '$CI_COMMIT_BRANCH == $CI_DEFAULT_BRANCH'
+      when: on_success
+    - if: '$CI_COMMIT_TAG =~ /^v\d+\.\d+\.\d+\-release/' # A specific tag with 'vX.Y.Z-release' pattern is created
+    - when: never
+#  release: # See https://docs.gitlab.com/ee/ci/yaml/#release for available properties
+#    tag_name: '$CI_COMMIT_TAG'
+#    description: '$CI_COMMIT_TAG'