Migrate GitHub automation to GitLab CI

.gitlab-ci.yml

@@ -0,0 +1,21 @@
+stages:
+  - test
+  - package
+  - release
+
+workflow:
+  rules:
+    - if: '$CI_PIPELINE_SOURCE == "merge_request_event"'
+    - if: '$CI_COMMIT_BRANCH && $CI_OPEN_MERGE_REQUESTS && $CI_PIPELINE_SOURCE == "push"'
+      when: never
+    - if: "$CI_COMMIT_BRANCH || $CI_COMMIT_TAG"
+
+variables:
+  RELEASE_VERSION:
+    value: ""
+    description: "Server image version to publish (strict SemVer, for example 3.1.0). Leave blank for a test-only pipeline."
+
+include:
+  - local: /.gitlab/ci/tests.yml
+  - local: /.gitlab/ci/container-release.yml
+  - local: /.gitlab/ci/desktop-release.yml