Remove defunct Mapi workflow

A contributor added this workflow to promote their service. But we never
found a use for it and at some point it broke because we didn't update
it. It has been disabled for two years now. Let's clean it up.

.github/workflows/mapi.yml

@@ -1,51 +0,0 @@
-name: 'Mayhem for API'
-on: workflow_dispatch
-permissions:
-  contents: read # to fetch code (actions/checkout)
-jobs:
-  test:
-    permissions:
-      contents: read # to fetch code (actions/checkout)
-      security-events: write # to upload SARIF results (github/codeql-action/upload-sarif)
-    if: ${{ github.repository_owner == 'openfoodfoundation' }}
-    runs-on: ubuntu-latest
-    strategy:
-      fail-fast: true
-    steps:
-    - uses: actions/checkout@v3
-    - run: docker/build
-    - run: docker compose up --detach
-    - run: until curl -f -s http://localhost:3000; do echo "waiting for api server"; sleep 1; done
-    - run: docker compose exec -T db psql postgresql://ofn:f00d@localhost:5432/open_food_network_dev --command="update spree_users set spree_api_key='testing' where login='ofn@example.com'"
-    # equivalent to Flipper.enable(:api_v1)
-    - run: docker compose exec -T db psql postgresql://ofn:f00d@localhost:5432/open_food_network_dev --command="insert into flipper_features (key, created_at, updated_at) values ('api_v1', localtimestamp, localtimestamp)"
-    - run: docker compose exec -T db psql postgresql://ofn:f00d@localhost:5432/open_food_network_dev --command="insert into flipper_gates (feature_key, key, value, created_at, updated_at) values ('api_v1', 'boolean', 'true', localtimestamp, localtimestamp)"
-
-    # Run Mayhem for API
-    - name: Run Mayhem for API
-      uses: ForAllSecure/mapi-action@v1
-      continue-on-error: true
-      with:
-        mapi-token: ${{ secrets.MAPI_TOKEN }}
-        api-url: http://localhost:3000
-        api-spec: swagger/v1.yaml
-        target: openfoodfoundation/openfoodnetwork
-        duration: 1min
-        sarif-report: mapi.sarif
-        html-report: mapi.html
-        run-args: |
-          --header-auth
-          X-Api-Token: testing
-
-    # Archive HTML report
-    - name: Archive Mayhem for API report
-      uses: actions/upload-artifact@v3
-      with:
-        name: mapi-report
-        path: mapi.html
-
-    # Upload SARIF file (only available on public repos or github enterprise)
-    - name: Upload SARIF file
-      uses: github/codeql-action/upload-sarif@v2
-      with:
-        sarif_file: mapi.sarif