LISK_API_PUBLIC=false does not work

[fchavant]

Expected behavior

Public API can be disabled by setting LISK_API_PUBLIC=false when LISK_NETWORK=devnet.

Actual behavior

LISK_API_PUBLIC=false does not seem to work with LISK_NETWORK=devnet.

Steps to reproduce

LISK_NETWORK=devnet node scripts/generate_config.js -c config.json |jq .modules.http_api.access.public
true
LISK_NETWORK=devnet LISK_API_PUBLIC=false node scripts/generate_config.js -c config.json |jq .modules.http_api.access.public
true

Which version(s) does this affect? (Environment, OS, etc...)

>=2.0

[nazarhussain]

Confirmed its because of this validation logic,

https://github.com/LiskHQ/lisk-sdk/blob/090e5a011ecaff59034da6b66ff7ae0e19474b0d/framework/src/controller/validator/keywords/env/index.js#L58

if (variableValue) {

This never triggered in case of false value. Rather it should be:

if (variableValue != undefined) {