Add instructions how setup automatic maven package deploy via CI

Signed-off-by: Dmitriy Zaporozhets <dmitriy.zaporozhets@gmail.com>

doc/user/project/maven_packages.md

@@ -52,4 +52,44 @@ You can add a corresponding section to your `settings.xml` file:
 </settings>
 ```  
 
+## Create maven packages with GitLab CI
+
+Once you have your repository configured to use GitLab Maven Packages repository, 
+you can configure GitLab CI to build new packages automatically. The example below 
+shows you how to create a new package each time the master branch is updated.
+
+1\. Create a `ci_settings.xml` file specially for GitLab CI and put it into your repository. 
+
+```xml
+<settings xmlns="http://maven.apache.org/SETTINGS/1.1.0" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
+  xsi:schemaLocation="http://maven.apache.org/SETTINGS/1.1.0 http://maven.apache.org/xsd/settings-1.1.0.xsd">
+  <servers>
+    <server>
+      <id>gitlab-maven</id>
+      <configuration>
+        <httpHeaders>
+          <property>
+            <name>Job-Token</name>
+            <value>CI_JOB_TOKEN</value>
+          </property>
+        </httpHeaders>
+      </configuration>
+    </server>
+  </servers>
+</settings>
+```
+
+2\. Add `deploy` section to your `.gitlab-ci.yml` file.
+
+```
+deploy:
+  script:
+    - 'cp ci_settings.xml /root/.m2/settings.xml'
+    - 'sed -i "s/CI_JOB_TOKEN/${CI_JOB_TOKEN}/g" /root/.m2/settings.xml'
+    - 'mvn deploy'
+  only:
+    - master
+  image: maven:3.3.9-jdk-8
+```
+
 [pat]: ../profile/personal_access_tokens.md