refs https://github.com/TryGhost/Admin/pull/2209
- `miragejs` has been extracted to a framework-independent library, the re-exports of `miragejs` elements in `ember-cli-mirage` have been deprecated making our test logs very noisy
- added `miragejs` as a top-level dependency
- updated all relevant imports to pull from `miragejs` instead of `ember-cli-mirage`
closes https://github.com/TryGhost/Team/issues/1320
- added `@allowEdit` argument to `<GhMemberLabelInput>` and changed the dropdown to only show the edit label when `@allowEdit` is truthy
- updated usage in the filter UI and members detail screens to allow editing
refs https://github.com/TryGhost/Team/issues/1320
- added a tracked `labels` property in `<ModalImportMembers::CsvFileMapping>` and passed it through to `<GhMembersLabelInput>` so that it has a list of labels that can be added to
- fixed error from sorting labels if one doesn't have a name
- added acceptance test for selecting labels in the members import flow
refs https://github.com/TryGhost/Team/issues/1320
- fixed event handling in `gh-file-input` for test-initiated uploads
- added `POST /members/upload/` API mock that emulates uploading a single member
- it's enough for this particular test and can be expanded as needed
- added acceptance test that does a simple 1-member, no Stripe, CSV upload with no mapping changes
refs https://github.com/TryGhost/Team/issues/1320
- start of acceptance tests ready for more detailed testing
- added ignore of `no-duplicate-landmark-elements` lint rule in import modal template
- the rule was a false flag because the conditionals only allow one `<header>` element to be rendered at a time
