Mock web api for dashboard tests (#1116)

* Add important comment into Github Workflow before running orion sever, about necessary `ulimit -n` to set so that MongoDB works correctly.

* Add a script to call orion server with requests.
Add script to Github workfloe 3 times.
Also run playwright 3 times.

* Add starting message, and request timeout (10 minutes).

* Remove urls.json, directly add urls into script.

* Try to increase ulimit -i, -l and -u

* Try to set soft ulimit

* Do not try anymore to set ulimit.

* Get back to PickledDB for frontend unit tests.

* Back to MongoDB.

* Add a fake server to mock orion server for dashboard tests.

* Use fake server in dashboard tests.

* Move back to original call_orion_server
Create gunicorn_tmp_dir in CI before launching fake server

* Clean-up and add doc.

.github/workflows/dashboard-src-new-with-playwright.yml

@@ -51,12 +51,12 @@ jobs:
     - name: check ulimit
       run: ulimit -a
 
-    - name: Start Orion backend
+    - name: Start fake Orion backend
       run: |
         # Start Orion backend in repository root folder.
         cd ../../
         mkdir -p gunicorn_tmp_dir
-        orion -vv serve -c .github/workflows/orion/orion_config_mongodb.yaml > dashboard/src/orion-backend-${{ matrix.node-version }}.log 2>&1 &
+        python .github/workflows/fake_orion_server.py > dashboard/src/fake-orion-backend-${{ matrix.node-version }}.log 2>&1 &
         cd dashboard/src/
 
     - name: Install dependencies
@@ -73,13 +73,22 @@ jobs:
     - name: Serve build
       run: ./node_modules/.bin/serve -l 3000 build/ &
 
-    - name: Run Playwright tests
+    - name: Run Playwright tests (1)
+      run: yarn playwright test --project=chromium --reporter=line
+
+    - name: Run Playwright tests (2)
+      run: yarn playwright test --project=chromium --reporter=line
+
+    - name: Run Playwright tests (3)
+      run: yarn playwright test --project=chromium --reporter=line
+
+    - name: Run Playwright tests (4)
       run: yarn playwright test --project=chromium --reporter=line
 
     # Upload orion backend log.
     - name: Get Orion backend log
       if: always()
       uses: actions/upload-artifact@v3
       with:
-        name: orion-backend-log-artifact-${{ matrix.node-version }}
-        path: dashboard/src/orion-backend-${{ matrix.node-version }}.log
+        name: fake-orion-backend-log-artifact-${{ matrix.node-version }}
+        path: dashboard/src/fake-orion-backend-${{ matrix.node-version }}.log