fix: add TestBench license setup to unit-tests job

Unit tests also require the TestBench Pro license to run. Add the
TB License configuration step to the unit-tests job, similar to the
integration-tests job.

Without this, unit tests that validate TestBench Pro features would
fail due to missing license configuration.

Author: Artur-

.github/workflows/validation.yml

@@ -99,6 +99,12 @@ jobs:
           path: ~/.m2/repository
           key: ${{ runner.os }}-maven-${{ hashFiles('**/pom.xml') }}-${{ github.run_id }}
 
+      - name: Set TB License
+        run: |
+          TB_LICENSE=${{secrets.TB_LICENSE}}
+          mkdir -p ~/.vaadin/
+          echo '{"username":"'`echo $TB_LICENSE | cut -d / -f1`'","proKey":"'`echo $TB_LICENSE | cut -d / -f2`'"}' > ~/.vaadin/proKey
+
       - name: Run unit tests
         run: |
           mvn test -B