* Track backend-only vars that are declared without a default value
Without this provision, declared backend vars can be accidentally shared among
all states if a mutable value is assigned to the class attribute.
* add test case for no default backend var
* lift node version restraint to allow more recent version if already installed
* add node test for latest version
* change python version
* use purple for debug logs
* update workflow
* add playwright dev dependency
* update workflow
* change test
* oops
* improve test
* update test
* fix tests
* mv units tests to a subfolder
* reorganize tests
* fix install
* update test_state
* revert node changes and only keep new tests organization
* move integration tests in tests/integration
* fix integration workflow
* fix dockerfile workflow
* fix dockerfile workflow 2
* fix shared_state
