PR: Fix the v3 -> v4 upload/download merging

.github/workflows/test-and-upload-coverage.yml

@@ -167,7 +167,16 @@ jobs:
         if: ${{ !matrix.detect-changes }}
         uses: actions/upload-artifact@v4
         with:
-          name: ${{ matrix.os }}_${{ matrix.client-type }}_${{ matrix.database-type }}_${{ matrix.mutation-type }}
+          # Make sure the name is always unique per job as artifacts are now immutable.
+          # Note Issue: https://github.com/actions/upload-artifact/issues/478
+          # Solve: https://github.com/actions/upload-artifact/issues/478#issuecomment-1885470013
+          name: coverage
+            _${{ matrix.os }}
+            _${{ matrix.client-type }}
+            _${{ matrix.database-type }}
+            _${{ matrix.mutation-type }}
+            _${{ matrix.lens-type }}
+            _${{ matrix.database-encryption }}
           path: coverage.txt
           if-no-files-found: error
           retention-days: 7
@@ -191,12 +200,17 @@ jobs:
       - name: Download coverage reports
         uses: actions/download-artifact@v4
         with:
+          pattern: coverage_*
+          # Note: https://github.com/actions/download-artifact/blob/main/docs/MIGRATION.md
+          # Solve: https://github.com/actions/upload-artifact/issues/478#issuecomment-1885470013
+          merge-multiple: true
           path: coverage_reports
 
       - name: Upload coverage to Codecov
         uses: codecov/codecov-action@v4
         with:
           token: ${{ secrets.CODECOV_TOKEN }}
+          files: coverage_reports/*.txt
           name: defradb-codecov
           flags: all-tests
           os: 'linux'