[Update] Subscriptions API + Facebook built-in browser

With MobilePay Subscriptions, it is easy to establish recurring payments. One way merchants can do so is by utilizing Facebook ad campaigns 

MobilePay has recently made some tweaks, that ensures that the MobilePay app opens from Facebook. We want to ensure that users do not leave the flow, if the MobilePay app isn't opened directly from the Facebook browser. 

Previously: MobilePay application is was not being opened from Facebook 's in-built browser.