Wallet messaging dev update from Hub21

Today working out of the Hub21 in Belgrade on the wallet messaging project. Discussed UX options for Service Provider and Wallet app handshake mechanism. The Wallet app needs to store the information about the Service Provider app's package name to be able to allow background payments for it and the Service Provider app needs to store the Wallet app package name so it can trigger it in the background. If the user chooses to enable background payments the Wallet app will send back with the result it's package name which the Service Provider app can choose to use for background payments or not.

Above option was one idea to do it but it seemed to involve more unnecessary steps. The main focus of this version is giving more control on the Service Provider side.

Note: Part of this UX might be usefull in the scenario where the user would have a section in the Service Provider app to "add a payment method" as you see with normal credit card payment methods.

This option is the one we decided to use for now. It's a simpler option for the use case where the payment is already being made and all of the necessary data to enable background payments is available.

Progress ✅

• Started initial implementation of UX option 1 handshake mechanism

Problems ✋

• We realized that you can't get the launching package name implicitly in the BroadcastReceiver when triggering it in the background. The Service Provider app will probably have to send it's package name when sending the payment request in the background

Next Plans 📆

• Complete the implementation of the handshake mechanism