refs https://github.com/TryGhost/Team/issues/1586
- updated `?newsletter_id=id` handling in posts API mock to match the real `?newsletter=slug` behaviour
- added additional publish flow acceptance tests for single/multiple newsletter behaviour, scheduling, and sending
refs https://github.com/TryGhost/Team/issues/1586
- added test helper for enabling/disabling members and helpers for disabling mailgun and newsletters
- added `loginAsRole` helper that alleviates duplication of user+role creation and also handles log-out before log-in so it's easier to mix different role tests within a block that has a default role setup in `beforeEach()`
- cleaned up editor tests that were skipped due to using the old publish flow
- added `Publish flow` acceptance test suite with an initial batch of tests
refs a021553203
- keeps text and logic together, avoids duplication of button code just for changing the running/success text
- added a `buttonTextMap` to keep the high-level text states in one place
- added `publishType` getter for easier switching between states in other getters and to have one place for the logic
- updated `confirmButtonText` getter and added `confirmRunningText` and `confirmSuccessText` getters that read from the button text map so the pattern used for getting text to pass as arguments in the template is consistent
