Messaging rewrite

[mmermerkaya]

I didn't want to leave the FCM SDK in it's current state, so I rewrote a large portion of it (and hopefully without any API changes this time 😄). There are also some API changes that I'd really like to do, like removing getToken and deleteToken from SWController or making vapidKey a parameter of getToken, but I guess they'll have to wait.

Changes:

• Composition over inheritance
  • Removed BaseController that the two main controllers were extending and moved the common parts to "token manager" module.
  • Removed DbInterface, which was not actually an interface but an abstract class, and the two classes that were extending it.
• Database
  • Moved Push API related fields to the subscriptionOptions subfield. This is now an optional field, as preparation for the eventual Safari support, which will not use the Push API.
  • Dropped swScope as an index, for the same reason as before.
  • Database key changed to App ID, as there should only be one token for every App ID. This should prevent "multiple messages received" issues in topic sends.
  • Created a new DB and added a migration function because the object store needed to change. This allowed removing the old DB code.
  • Started using the battle-tested IndexedDB library idb, which is already being used in Installations.
• Size reduction
  • Non minified ES5 ESM build is now 70.8kB. Old one was 96.8kB.
  • Minified and gzipped ES5 build is now 10.1kB. Old one was 12.5kB.
• Tests
  • Increased coverage from 93% to 99%. Coveralls reports a drop in coverage because I also changed the coverage config to stop including test files in coverage reports.
  • Made the tests more meaningful by removing all private member access from tests. Focusing on testing behavior, not implementation.
  • Added complete Service Worker fakes to use with every test. Removed messing with prototype objects in fakes.
  • Removed the uses of any type from tests. There used to be 83 instances of type any in tests.
• Structure and Naming:
  • Greatly reduced the number of classes. Not everything needs to be a class.
  • Combined src/ and test/ folders, following our style guide.
  • Removed the -model suffix. More meaningful names overall.

[dwoffinden]

Awesome work! :D