Default UI: Legacy for existing merchants, React for new merchants (4030)

[Narek13]

Issue Description

Current situation
When the feature flag for the new UI is enabled, all merchants instantly see the new onboarding wizard and settings screens.

Expected

• When the feature flag is enabled, existing merchants should still get the legacy settings UI, with a new button/toggle to enable the new UI.
  • Those users should not see the onboarding wizard, but directly get the settings pages
• All new merchants (i.e. fresh installations) should instantly see the new UI, starting with the onboarding wizard.

PR Description

The PR will cover the following scenarios when the feature flag for the new UI is enabled:

• All the new merchants (i.e. fresh installations) will instantly see the new UI, starting with the onboarding wizard.
• existing merchants will still get the legacy settings UI, with a new button/toggle to enable the new UI.
  • If onboarded, will not see the onboarding wizard, but directly get the settings pages

[danieldudzic]

@Narek13 Looking good!

I have noticed that when I select the "Switch to new settings UI" button, it doesn't do anything, and throws an error in the console:

The page correctly then displays the new settings UI, after a page reload.

The new UI should show up straight after selecting the button.

[Narek13]

@danieldudzic I cannot reproduce, works fine for me, once clicked on the button, the page reloads with the new settings. Did you build the scripts? Maybe someone else also can check this. @stracker-phil @Dinamiko

[danieldudzic]

@Narek13 Ok, I have now identified the issue. With WP_DEBUG active it was being caused by: #2816

[danieldudzic]

All good!