PayPal declares subscription support when merchant not enabled for Reference Transactions (2068)

[stracker-phil]

Summary:

Since version 2.3.0-rc2 of the WooCommerce Subscriptions plugin, PayPal subscriptions cannot be disabled if the merchant is not enabled for Reference Transactions (RT, also known as "vaulting").

Technical Details:

• The issue arises because the database setting value for Subscription Mode is incorrectly saved as subscriptions_api, regardless of the selected option.
• The correct value is sent from the browser (visible via the network tab), but it gets reset when saving the settings page.

Expected Behavior:

• When the connected PayPal merchant is not enabled for RT and the Subscriptions Mode is set to "Disable PayPal for subscriptions", the PayPal gateway should not declare support for subscriptions.

Fix Implemented:

• Corrected the logic to ensure the proper value is saved and retained in the database for the Subscriptions Mode setting.
• Verified that the correct value is sent from the browser and saved in the database, preventing it from resetting to subscriptions_api.