Streamline GitLab API URL variables

The Platform and the Janitor now share a single variable in the Helm values file global.gitlabApiUrl for the GitLab URL. The handling of the GitLab API secret has been reworked too. The Secret resource has been renamed from nmaas-gitlab-janitor-token to nmaas-gitlab-api-token. Additionally it has been moved to global.gitlabApiToken. Old deployment can choose to manually specify global.gitlabApiToken.secret.name to the old value of nmaas-gitlab-janitor-token in order not to create a new secret.

.github/workflows/build-chart.yaml

-name: Build NMaaS Helm Chart
-on:
-  push:
-    branches:
-      - '**'
-jobs:
-  test_chart:
-    runs-on: ubuntu-22.04
-    steps:
-      - name: Checkout
-        uses: actions/checkout@v3
-        with:
-          fetch-depth: "0"
-
-      - uses: actions/setup-python@v2
-        with:
-          python-version: 3.8
-
-      - name: Set up Helm
-        uses: azure/setup-helm@v3
-        with:
-          version: v3.9.2
-
-      - name: Set up chart-testing
-        uses: helm/chart-testing-action@v2.3.1
-
-      - name: Add Helm repository
-        run: helm repo add nmaas-helm-mirror https://artifactory.software.geant.org/artifactory/nmaas-helm-mirror
-
-      - name: Lint Helm chart
-        run: ct lint --debug --target-branch master
-
-      - name: Check for chart changes
-        id: list-changed
-        run: |
-          changed=$(ct list-changed --target-branch master)
-          if [[ -n "$changed" ]]; then
-            echo ::set-output name=changed::true
-          fi
-
-      - name: Install helm-docs
-        run: |
-          if [ not $(which helmd-docs) ]
-          then
-            mkdir -p ~/.local/bin
-            wget -O /tmp/helm-docs.tar.gz https://github.com/norwoodj/helm-docs/releases/download/v1.11.0/helm-docs_1.11.0_Linux_x86_64.tar.gz
-            tar -xvzf /tmp/helm-docs.tar.gz -C ~/.local/bin
-            rm ~/.local/bin/README.md ~/.local/bin/LICENSE
-            echo "${HOME}/.local/bin" >> $GITHUB_PATH
-          fi
-        shell: bash
-        if: steps.list-changed.outputs.changed == 'true'
-
-      - name: Generate helm-docs
-        run: helm-docs --output-file ../../README.md
-        if: steps.list-changed.outputs.changed == 'true'
-
-      - name: Commit changes made to readme files
-        uses: stefanzweifel/git-auto-commit-action@v4
-        with:
-          commit_message: update chart readme.md files automatically
-        if: steps.list-changed.outputs.changed == 'true'
\ No newline at end of file