isTruthyEnvValue function
Whether an FA_* boolean env value counts as ON — the repo-wide
truthy convention (introduced for piModeEnvVar): '1'/'true'/'yes'/ 'on', case-insensitive, trimmed; any other value (including 0,
false, "") is OFF. ONE helper for every FA_* switch (issue #778
round 2): FA_PI_MODE and FA_NO_FORMAT must never diverge.
Implementation
bool isTruthyEnvValue(String? value) =>
_truthyEnvValues.contains(value?.trim().toLowerCase());