Use special Maven settings with access token to GitHub Packages

The access token is for the 'kriegaex' account. Can be adjusted or
extended in order to support other Package registries, too. for now, I
just want to see it this solves the authentication error problems during
GitHub CI builds.

The new file .mvn/settings-read-github-packages.xml contains additional
information and links to online sources, explaining why this is
necessary.

Signed-off-by: Alexander Kriegisch <Alexander@Kriegisch.name>

.github/workflows/maven.yml

@@ -32,14 +32,14 @@ jobs:
           ant -version
 
       - name: Download + install test libraries
-        run: ./mvnw -B -U --file libx/pom.xml compile
+        run: ./mvnw -B --settings .mvn/settings-read-github-packages.xml --file libx/pom.xml compile
 
       - name: Compile + package code
-        run: ./mvnw -B -DskipTests package --file pom.xml
+        run: ./mvnw -B --settings .mvn/settings-read-github-packages.xml --file pom.xml -DskipTests package
 
       - name: Run Tests
         # Tests in module ajde call Swing/AWT classes. Without frame buffer they throw
         # HeadlessException: No X11 DISPLAY variable was set, but this program performed an operation which requires it.
         uses: GabrielBB/xvfb-action@v1
         with:
-          run: ./mvnw -B -Daspectj.tests.verbose=false verify --file pom.xml
+          run: ./mvnw -B --settings .mvn/settings-read-github-packages.xml --file pom.xml -Daspectj.tests.verbose=false verify

.mvn/settings-read-github-packages.xml

@@ -0,0 +1,25 @@
+<settings xmlns="http://maven.apache.org/SETTINGS/1.0.0" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
+  xsi:schemaLocation="http://maven.apache.org/SETTINGS/1.0.0 https://maven.apache.org/xsd/settings-1.0.0.xsd">
+
+<!--
+  GitHub Actions currently requires authentication even for read-only access to Maven artifacts stored in GitHub
+  Packages. There is no such thing as public package repositories without authentication. See here:
+  https://github.community/t/how-to-allow-unauthorised-read-access-to-github-packages-maven-repository/115517/4
+
+  How to use it:
+  https://github.com/jcansdale-test/maven-consume
+
+  How to XML-encode an access token online (no problem to use the website, it is meant for public access anyway):
+  https://coderstoolbox.net/string/#!encoding=xml&action=encode&charset=none
+-->
+
+  <servers>
+    <server>
+      <id>github</id>
+      <username>kriegaex</username>
+      <!-- Public access token with 'read:packages' scope -->
+      <password>&#103;&#104;&#112;&#95;&#68;&#74;&#97;&#71;&#119;&#108;&#80;&#75;&#55;&#116;&#68;&#55;&#102;&#73;&#51;&#107;&#103;&#111;&#109;&#71;&#100;&#78;&#115;&#86;&#105;&#88;&#67;&#100;&#50;&#98;&#50;&#55;&#74;&#104;&#66;&#77;</password>
+    </server>
+  </servers>
+
+</settings>