OZG-4097 pipeline: Add docker authentication

.gitlab-ci.yml

@@ -12,6 +12,28 @@ variables:
 services:
   - docker:dind
 
+before_script:
+  - mkdir -p $HOME/.docker
+  - |
+    cat << EOF > $HOME/.docker/config.json
+    {
+      "auths": {
+        "docker.ozg-sh.de": {
+          "username": "$NEXUS_USER",
+          "password": "$NEXUS_PASSWORD"
+        }
+      },
+      "proxies": {
+        "default": {
+          "httpProxy": "$HTTP_PROXY",
+          "httpsProxy": "$HTTPS_PROXY",
+          "noProxy": "$NO_PROXY"
+        }
+      }
+    }
+    EOF
+  - cat ~/.docker/config.json
+
 cache:
   paths:
     - .m2/repository/