isProviderManagedEnvVar function
Check if a key is a provider-managed env var.
Implementation
bool isProviderManagedEnvVar(String key) {
final upper = key.toUpperCase();
if (_providerManagedEnvVars.contains(upper)) return true;
for (final prefix in _providerManagedEnvPrefixes) {
if (upper.startsWith(prefix)) return true;
}
return false;
}