API does not error out/apply default for environment variable set to empty string

[alyssadai]

For our required environment variables in the n-API, e.g., NB_GRAPH_USERNAME, we have a startup checks that they are set using syntax like the following:

api/app/main.py

Lines 99 to 100 in 3718200

	os.environ.get(util.GRAPH_USERNAME.name) is None
	or os.environ.get(util.GRAPH_PASSWORD.name) is None

However, this check only works if the variable does not exist in the environment at all, and does not catch cases where the variable exists but is set to an empty string "" (such as the default docker compose behaviour if an interpolated variable defined in environment is unset).

More sneakily, this docker compose behaviour also affects other environment variables that are optional but which we expect to apply the n-API to apply a sensible default for, such as NB_MIN_CELL_SIZE. Since docker-compose.yml does not assign a default value, this variable is automatically set to "", meaning that the API no longer detects it as being unset. This results in unpredictable values for variables inside the n-API.

• Related to Unset minimum cell size in .env file leads to undeployable stack recipes#111

Steps to resolve

• Following Refactor environment variable reading using pydantic-settings #316, we can probably use the env_ignore_empty config option in our new API settings class to prevent this from happening across all variables

[alyssadai]

Blocked by #316