Upgrade to Gradle 7.6, switch to maven-publish plugin, upgrade credentials plugin

Author: mrotteveel

.github/workflows/gradle.yml

@@ -28,7 +28,24 @@ jobs:
       with:
         java-version: '11'
         distribution: 'temurin'
+        cache: gradle
+    - name: Validate Gradle wrapper
+      uses: gradle/wrapper-validation-action@55e685c48d84285a5b0418cd094606e199cca3b6
     - name: Build with Gradle
       uses: gradle/gradle-build-action@0d13054264b0bb894ded474f08ebb30921341cee
       with:
         arguments: build
+    - name: Cleanup Gradle Cache
+      # Remove some files from the Gradle cache, so they aren't cached by GitHub Actions.
+      # Restoring these files from a GitHub Actions cache might cause problems for future builds.
+      run: |
+        rm -f ~/.gradle/caches/modules-2/modules-2.lock
+        rm -f ~/.gradle/caches/modules-2/gc.properties
+        rm -fr ~/.gradle/caches/*/plugin-resolution/
+        find ~/.gradle/caches/ -name "*.lock" -type f -delete
+    - name: build artifact
+      uses: actions/upload-artifact@v3
+      with:
+        name: build-artifacts
+        path: build/libs
+        retention-days: 1