Notification service

[NejcZdovc]

When we receive new event that is worth showing to the user (list below) we need to send it to the url bar icon. We should create observable that url bar can use.

Related issue #921

Notifications:

• auto contribute (when contribution is done)
• token grant (when new grant is available)
• error for failed contribution
• 1 day before contribution
• 3 days before if you don't have enough funds

@davidtemkin should we also show when recurring donation is done?

[davidtemkin]

Auto contribute should occur on the same cycle as recurring donations - so the event is the same @NejcZdovc

We also need to notify when the scheduled contribution fails -- i.e., not enough funds to cover the total of auto-contribute monthly budget + total of all recurring donations

[NejcZdovc]

@davidtemkin added to the list