Breaking change: Updated ConfigScope.getOptional to fallback to default value when environment variable is an empty string ('')

[fl-lokalise]

Changes

Problem statement

Given

VAR1=
VAR2=

and performing

var1: configScope.getOptionalInteger('VAR1', 42),
var2: configScope.getOptional('VAR2', 'foo'),

the produced configuration has inconsistent fallback behavior

{
    var1: 42,
    var2: '',
}

Proposed solution

Use logical OR operator || instead of ?? in ConfigScope.getOptional.

Notes

Taking into account that `configScope.getOptional('VAR2', 'foo') currently returns an empty string, this change has the ability to break an application.
Both for applications that rely on this behaviour and the ones that were not aware of this fallback behaviour.

Checklist

• Apply one of following labels; major, minor, patch or skip-release
• I've updated the documentation, or no changes were necessary
• I've updated the tests, or no changes were necessary