fix: add integration tests with auth

[ividito]

Issue

No directly related issue, this came out of work on #497

What?

• Add integration tests that use local auth mocks to hit authenticated transactions endpoints

Why?

• Makes it easier to test changes to transactions endpoints locally without messing around too much with auth configuration

Testing?

# run stack with transactions enabled
docker compose -f docker-compose.yml -f docker-compose.transactions.yml
# run tests
pytest .github/workflows/tests/test_transactions.py