test: split the backend suite by domain; CI discovers tests/backend (#141)

Author: gorevds

.github/workflows/test.yml

@@ -23,7 +23,7 @@ jobs:
           python-version: ${{ matrix.python-version }}
       - if: matrix.crypto == 'with'
         run: pip install 'cryptography>=42'
-      - run: python test_server.py -v
+      - run: python -m unittest discover -s tests/backend -t . -v
 
   frontend:
     runs-on: ubuntu-latest