Add support for cashq push notifications

[adonese]

I have always been resilient to the idea of adding push notifications, but a business need has emerged that makes it important to add push notifications

https://documentation.onesignal.com/docs/onesignal-api

[adonese]

We started rolling out push notification service for cashq.

This issue will be used to track the progress of app implementation for cashq.

• we have background pushes (handled by the os)
• we have foreground pushes (currently not implemented)

We should:

• fork the result.class
• add support for online pushes
• integrate with deep links to link the push with the app

[adonese]

We decided to go with firebase notifications as oppose of onesignal or other providers.