Upgrade to the latest dependencies

* Upgrade to Gradle `7.6`
* Apply Spring Integration code style
* Replace obsolete Travis CI with GitHub Actions
* Fix test XML configs for the latest Mockito

.github/workflows/pr-build-workflow.yml

@@ -0,0 +1,33 @@
+name: Pull Request build
+
+on:
+  pull_request:
+    branches: [ main ]
+
+jobs:
+  build:
+
+    runs-on: ubuntu-latest
+
+    steps:
+
+      - uses: actions/checkout@v3
+
+      - name: Set up JDK
+        uses: actions/setup-java@v3
+        with:
+          distribution: 'temurin'
+          java-version: 17
+
+      - name: Run Gradle
+        uses: gradle/gradle-build-action@v2
+        with:
+          arguments: check
+
+      - name: Capture Test Results
+        if: failure()
+        uses: actions/upload-artifact@v3
+        with:
+          name: test-results
+          path: '*/build/reports/tests/**/*.*'
+          retention-days: 3